Journal of Autism and Developmental Disorders Vol. 29, No. 6, 1999
The Screening and Diagnosis of Autistic Spectrum Disorders1
Pauline A. Filipek,2,17 Pasquale J. Accardo,3 Grace T. Baranek,4 Edwin H. Cook, Jr.,5
Geraldine Dawson,6 Barry Gordon,7 Judith S. Gravel,8 Chris P. Johnson,9
Ronald J. Kallen,5 Susan E. Levy,10 Nancy J. Minshew,11 Barry M. Prizant,12
Isabelle Rapin,8 Sally J. Rogers,13 Wendy L. Stone,14 Stuart Teplin,4
Roberto F. Tuchman,15 and Fred R. Volkmar16
The Child Neurology Society and American Academy of Neurology recently proposed to for-
mulate Practice Parameters for the Diagnosis and Evaluation of Autism for their memberships.
This endeavor was expanded to include representatives from nine professional organizations and
four parent organizations, with liaisons from the National Institutes of Health. This document
was written by this multidisciplinary Consensus Panel after systematic analysis of over 2,500
relevant scientific articles in the literature. The Panel concluded that appropriate diagnosis of
autism requires a dual-level approach: (a) routine developmental surveillance, and (b) diagno-
sis and evaluation of autism. Specific detailed recommendations for each level have been es-
tablished in this document, which are intended to improve the rate of early suspicion and diag-
nosis of, and therefore early intervention for, autism.
The synonymous terms Autistic Spectrum Dis-
orders and Pervasive Developmental Disorders refer
to a wide continuum of associated cognitive and neuro-
behavioral disorders, including, but not limited to, three
Portions of this manuscript were reproduced with permission from Fil-
ipek, P. A. (1999). The autistic spectrum disorders. In K. F. Swaiman
& S. Ashwal (Eds.), Pediatric neurology. Principles and practice
(3rd ed., pp. 606-628). St. Louis, MO: Mosby
1 With the exception of the first author, all authors are listed in al-
2 University of California, Irvine, Irvine, California 92717.
3 New York Medical College, Valhalla, New York 10595.
4 University of North Carolina at Chapel Hill, Chapel Hill, North
5 University of Chicago, Chicago, Illinois 60637-1513.
6 University of Washington, Seattle, Washington 98195.
7 Johns Hopkins University School of Medicine, Baltimore, Maryland
8 Albert Einstein College of Medicine, Bronx, New York.
9 University of Texas Health Science Center at San Antonio, San
Antonio, Texas 78284-8200.
core-defining features: impairments in socialization,
impairments in verbal and nonverbal communication,
and restricted and repetitive patterns of behaviors
(American Psychiatric Association [APA], 1994).
Many terms have been used over the years to refer to
these disorders, (e.g., infantile autism, pervasive de-
velopmental disorder- residual type, childhood schizo-
phrenia, and autistic psychoses). Although autism was
10 University of Pennsylvania School of Medicine, Philadelphia,
11 University of Pittsburgh School of Medicine, Pittsburgh, Penn-
12 Brown University, Providence, Rhode Island 02912.
13 University of Colorado Health Science Center, Denver, Colorado
14 Vanderbilt University Medical Center, Nashville, Tennessee.
15 University of Miami School of Medicine, Coral Gables, Florida.
16 Yale University, New Haven, Connecticut 06520.
17 Address all correspondence to Pauline A. Filipek, Departments of
Pediatrics and Neurology, University of California, Irvine, College
of Medicine, UCI Medical Center, Route 81-4482, 101 City Drive
South, Orange, California 92868-3298; e-mail: email@example.com.
0162-3257/99/1200-0439$ 16.00/0 © 1999 Plenum Publishing Corporation
KEY WORDS: Practice parameters diagnosis and evaluation of autism; dual-level approach.
Filipek et al.
first described over 50 years ago by Kanner (1943), our
improved understanding of this complex disorder has
emerged over the past two decades, and, despite the re-
cent intense focus on autism, it continues to be an art
and science in rapid evolution.
The terms autism, autistic, and autistic spectrum
disorders are used interchangeably throughout this paper
and refer to the broader umbrella of pervasive develop-
mental disorders (PDD), whereas the specific term Autis-
tic Disorder is used in reference to the more restricted
criteria as defined by the Diagnostic and Statistical Man-
ual of Mental Disorders, 4th Edition (DSM-IV; APA,
1994). The complexity and wide variability of symptoms
within the autistic spectrum point to multiple etiologies
which are currently grouped together under this diag-
nostic umbrella because of the similar core behavioral
The autistic spectrum disorders are not rare disor-
ders, but instead are more prevalent in the pediatric pop-
ulation than cancer, diabetes, spina bifida, and Down syn-
drome. The earliest epidemiology studies noted a
prevalence of Infantile Autism of 4-5 per 10,000 which
is approximately 1 in every 2,000 people (Lotter, 1966).
With the broader clinical phenotype and improved clin-
ical recognition, the prevalence estimates have increased
to 10-20 per 10,000, or one in every 500 to 1,000 peo-
ple (Bryson, 1996; Bryson, Clark, & Smith, 1988a; Ehlers
& Gillberg, 1993; Gillberg, Steffenburg, & Schaumann,
1991; Ishii & Takahasi, 1983; Sugiyama & Abe, 1989;
Wing & Gould, 1979). Recent statistical analyses by the
Commonwealth of Massachusetts Department of Public
Health indicate a prevalence rate in the Zero-to-Three
Early Intervention Program of 1 in 500 children (Tracey
Osbahr, Massachusetts DPH, personal communication,
March 1999). These higher prevalence rates imply that
there are between 60,000 and 115,000 children under
15 years of age in the United States who meet diagnos-
tic criteria for autism (Rapin, 1997). Most recently, Baird
et al. (1999) found a prevalence rate of 30.8 cases per
10,000 of Autistic Disorder (1 in 333 children), with 27.1
additional cases per 10,000 for the autistic spectrum dis-
orders. These prevalence rates are significantly higher
than those noted in previous reports and require reconfi-
mation in a future study. However, the notion of these
markedly increasing prevalence rates further affirms the
need for improved early screening and diagnosis.
The overall ratio of males to females with autism has
traditionally been reported at approximately 3:1 to 4:1
(Lotter, 1966; Wing & Gould, 1979). However, the ratio
seems to vary with IQ, ranging from 2:1 with severe dys-
function to more than 4:1 in those with average IQ
(Bryson, 1997; Ehlers & Gillberg, 1993; Wing & Gould,
1979). Some feel that fewer females with normal IQ are
diagnosed with autism because they may be more socially
adept than males with similar IQ (McLennan, Lord, &
Schopler, 1993; Volkmar, Szatmari, & Sparrow, 1993b).
Every health care or educational agency serving
young children can expect to see children with autism.
Although symptoms of autism may be present in the first
year of life in children who are diagnosed later, and
symptoms are virtually always present before the age of
3 years, autism is often not diagnosed until 2 to 3 years
after symptoms appear. Individuals with autism also
often remain undiagnosed or inaccurately diagnosed.
Many clinicians hesitate to discuss the possibility of a
diagnosis of autism with parents of young children even
when some symptoms are present, due to concerns about
family distress, the possible adverse effects of labeling
a child, the possibility of being incorrect, or the hope
that the symptoms will reverse over time. However, it is
believed that the positive outcomes of accurate diagno-
sis far outweigh the negative effects, and families uni-
versally express the desire to be informed as early as
possible (Marcus & Stone, 1993).
In actuality, the advantages of early diagnosis of
autism are many and include earlier educational plan-
ning and treatment, provision for family supports and
education, reduction of family stress and anguish, and
delivery of appropriate medical care to the child (Cox
et al., 1999). Screening activities are crucial to early
diagnosis. The purpose of screening is to identify chil-
dren at risk for autism as soon as possible so that they
can be rapidly referred for full diagnostic assessment
and needed interventions. The press for early identi-
fication comes from evidence gathered over the past
10 years that intensive early intervention in optimal
educational settings results in improved outcomes in
most young children with autism, including speech in
75% or more and significant increases in rates of de-
velopmental progress and intellectual performance
(Dawson & Osterling, 1997; Rogers, 1996, 1998).
However, these kinds of outcomes have been docu-
mented only for children who receive 2 years or more
of intensive intervention services during the preschool
years (Anderson, Avery, Dipietro, Edwards, & Chris-
tian, 1987; Anderson, Campbell, & Cannon, 1994;
Fenske, Zalenski, Krantz, & McClannahan, 1985;
Hoyson, Jamieson, & Strain, 1984; Lovaas, 1987;
McEachin, Smith, & Lovaas, 1993; Ozonoff & Cath-
cart, 1998). Thus, early screening and early identifi-
cation are crucial for improving outcomes of children
with autism (Hoyson et al., 1984; McEachin et al.,
1993; Rogers, 1996, 1998, in press; Rogers & Lewis,
1989; Sheinkopf & Siegel, 1998).
Howlin and Moore (1997) described the diagnostic
experiences of almost 1,300 families with children with
Screening and Diagnosis of Autistic Spectrum Disorders
autism from the United Kingdom. The average age at
diagnosis in this study was not until 6 years (while in
the U.S. the average is 3 to 4 years of age), despite the
fact that most if not all parents of children with autism
had a sense that something was wrong by 18 months of
age on average and usually first sought medical assis-
tance by 2 years of age. The U.K. parents reported that
despite concerns in at least three different developmen-
tal areas, fewer than 10% were given a diagnosis at ini-
tial presentation. About 90% were referred to another
professional (at a mean age of 40 months). Twenty-five
percent were nonetheless told "not to worry." In the re-
maining 10%, over half were told to return if their wor-
ries persisted, and the rest were told that their child
"would grow out of it." Of those families referred to a
second professional, only 40% were given a formal di-
agnosis and 25% were referred to yet a third or fourth
professional. Almost 25% of the families were either re-
assured by the second professional and told not to worry,
or their concern was acknowledged but no further action
was taken. Almost 20% reported that they either had to
exert considerable pressure to obtain the referrals or pay
privately. Over 30% of parents referred to subsequent
professionals reported that no help was offered (e.g., with
education, therapy, or referrals to parent support groups),
and only about 10% reported that a professional ex-
plained their child's problems. Almost half of the fam-
ilies reported that the school system and other parents
were the major source of assistance over time, rather
than the medical health care community.
Howlin and Moore (1997) concluded that (a) early
parental concerns about a child's development should be
taken more seriously by both primary care and special-
ist professionals, with speedy referrals to appropriate fa-
cilities, (b) labels such as "autistic tendencies" or "fea-
tures" should be avoided if one is unable to give a
specific diagnosis of autism, and that (c) diagnosis in it-
self may be a critical step but will not improve progno-
sis unless combined with practical help and support to
assist parents in obtaining treatment for the child, in
order to develop skills and strategies applicable through-
out the child's life.
lescent Psychiatry, American Academy of Family Physi-
cians, American Academy of Neurology, American
Academy of Pediatrics, American Occupational Therapy
Association, American Psychological Association, Amer-
ican Psychological Society, American Speech-Language
Hearing Association, Child Neurology Society, Society
for Developmental and Behavioral Pediatrics, and the
Society for Developmental Pediatrics for representa-
tive(s) from each organization with the requisite expert-
ise in the screening and diagnosis of autism, whether by
clinical research or clinical practice.
Final representatives include Judith S. Gravel
(American Academy of Audiology); Edwin H. Cook Jr.
and Fred R. Volkmar (American Academy of Child and
Adolescent Psychiatry); Isabelle Rapin and Barry Gor-
don (American Academy of Neurology); Stuart Teplin,
Ronald J. Kallen, and Chris Plauche Johnson (Ameri-
can Academy of Pediatrics); Grace T. Baranek (Amer-
ican Occupational Therapy Association); Sally J. Rogers
and Wendy L. Stone (American Psychological Associ-
ation); Geraldine Dawson (American Psychological So-
ciety); Barry M. Prizant (American Speech-Language
Hearing Association); Nancy J. Minshew and Roberto
F. Tuchman (Child Neurology Society); Susan E. Levy
(Society for Developmental and Behavioral Pediatrics);
and Pasquale J. Accardo (Society for Developmental
Pediatrics). Representatives were named from the fol-
lowing associations: Barbara Cutler and Susan Good-
man (Autism National Committee), Cheryl Trepagnier
(Autism Society of America), Daniel H. Geschwind
(Cure Autism Now), and Charles T. Gordon (National
Alliance for Autism Research). The National Institutes
of Health also named liaisons to serve on this commit-
tee, including Marie Bristol-Power (National Institute
of Child Health and Human Development), Judith
Cooper (National Institute of Deafness and Communi-
cation Disorders), Judith Rumsey (National Institute of
Mental Health), and Giovanna Spinella (National Insti-
tute of Neurological Disorders and Stroke).
Consensus was reached by group discussion in all
cases, either including the entire panel, or within sub-
groups by specialities.
DESCRIPTION OF THE ANALYTICAL
Selection of Consensus Panel
Filipek was named by the American Academy of
Neurology to chair a committee to determine practice
parameters for screening and diagnosis of autism. Nom-
inations were then sought from the American Academy
of Audiology, American Academy of Child and Ado-
Comprehensive computerized literature searches of
Medline (National Library of Medicine) and PsychINFO
(American Psychological Association) in all languages
using the terms "(autistic OR autism OR pervasive)
NOT treatment" produced over 4,000 documents. The
focus was on literature published since 1990 that re-
ported scientific research, but older sources and less
stringent studies were included when relevant. A bibli-
Filipek et al.
Pervasive Developmental Disorder. In DSM-III, autism
was also clearly differentiated from childhood schizo-
phrenia and other psychoses for the first time, and the
absence of psychotic symptoms, such as delusions and
hallucinations, became one of the six diagnostic criteria.
The revised DSM-III-R (APA, 1987) broadened the PDD
spectrum and narrowed the possible diagnoses to two,
Autistic Disorder and Pervasive Developmental Dis-
orderNot Otherwise Specified (PDD-NOS).
Currently, DSM-IV (APA, 1994) includes five pos-
sible diagnoses under the PDD umbrella (Table I) which
are concordant with the International Classification of
Disease, 10th edition (ICD-10), used primarily abroad
(World Health Organization [WHO], 1992).
The Broader Phenotype
Although Allen first coined the phrase "autistic
spectrum disorder" (1988), the same year that Wing
wrote about the "autistic continuum" (1988), controversy
still surrounds this concept of a broader clinical pheno-
type. DSM-III (APA, 1980) acknowledged that such a
continuum existed, and labeled it PDD; the term Autis-
tic Disorder was reserved only for those with classical
signs and symptoms presenting before 30 months of age.
Over the past 10 years, however, there has been a slowly
growing clinical consensus that the umbrella of "perva-
sive developmental disorders" does actually represent an
"autistic spectrum" (Wing, 1997). For the first time,
DSM-IV criteria included the term qualitative to describe
the impairments within the major criteria, defining a
range of impairments rather than the absolute presence
or absence of a particular behavior as sufficient to meet
a criterion for diagnosis.
Table I. The Pervasive Developmental (Autistic Spectrum)
(WHO, 1992, 1993)
Other childhood disintegrative
Overactive disorder with
mental retardation with
a PDD-NOS = Pervasive Developmental Disorder-Not Otherwise
ography of over 2,750 references was developed for this
review; article abstracts were initially reviewed, fol-
lowed by the relevant articles in entirety. The review
process was expedited by the many review papers and
meta-analyses developed for DSM-IV (APA, 1994), the
research overview resulting from the National Institutes
of Health State of the Science Conference on Autism in
1995 (see Bristol et al., 1996, and accompanying arti-
cles) and current review articles, book chapters and
books (Bailey, Phillips, & Rutter, 1996; Bauer, 1995a,
1995b; D. J. Cohen & Volkmar, 1997; Filipek, 1999;
Minshew, 1996a; Minshew, Sweeney, & Bauman, 1997;
Rapin, 1997; Rutter, 1996).
Autism from 1943 to 1980
Kanner (1943) first described a syndrome of "autis-
tic disturbances" with case histories of 11 children who
presented between the ages of 2 and 8 years and who
shared "unique" and previously unreported patterns of
behavior including social remoteness, obsessiveness,
stereotypy, and echolalia. After its initial description,
autism was poorly ascertained during the middle decades
of the 20th century. In DSM-I (APA, 1952) and DSM-
II (APA, 1968), "psychotic reactions in children, mani-
festing primarily autism," were classified under the terms
"schizophrenic reaction or schizophrenia, childhood
type" (p. 28).
Despite this early but persisting view of autism as
a psychosis, several prominent research groups formu-
lated the first set of diagnostic criteria for this disorder
by the 1970s (Ritvo & Freeman, 1978; Rutter & Hersov,
1977). With DSM-III (APA, 1980), the term Pervasive
Developmental Disorders (PDD) was first used to
characterized by distortions in the development of mul-
tiple basic psychological functions that are involved in
the development of social skills and language, such as
attention, perception, reality testing, and motor move-
ment . . . The term Pervasive Developmental Disorder
was selected because it describes most accurately the
core clinical disturbance: many basic areas of psycho-
logical development are affected at the same time and
to a severe degree. (p. 86)
Under this new PDD umbrella, the possible diagnoses
included, for the first time, the term Infantile Autism
(with onset prior to age 30 months) as well as Childhood
Onset Pervasive Developmental Disorder (with onset
after age 30 months), each further subclassified into "Full
Syndrome Present" or "Residual State," and Atypical
Screening and Diagnosis of Autistic Spectrum Disorders
The currently recognized clinical phenotype in-
cludes children with milder, but nonetheless unequivo-
cal, social, communication, and behavioral deficits. Many
high-functioning autistic children are diagnosed after
presentation to clinics specializing in learning disabili-
ties or Attention-Deficit/Hyperactivity Disorder (ADHD)
(Porter, Goldstein, Galil, & Carel, 1992). Almost 15%
of previously undiagnosed children receiving special ed-
ucation services met criteria for DSM-III-R Autistic Dis-
order in one series (Deb & Prasad, 1994). Autistic "traits"
were also retrospectively found in almost one quarter of
2,201 adults previously diagnosed with various learning
disabilities (Bhaumik, Branford, McGrother, & Thorp,
1997). Questionnaires devised to specifically diagnose
ADHD will not identify autistic symptomatology, and
74% of children with high-functioning autism in another
series had erroneously been previously diagnosed with
ADHD despite clear differences in their social compe-
tence, cognitive development, and restricted range of ac-
tivities (Jensen, Larrieu, & Mack, 1997).
PRESENTING SIGNS AND SYMPTOMS OF
THE AUTISTIC SPECTRUM DISORDERS
All children on the autistic spectrum demonstrate
the same core deficits, in (a) reciprocal social interactions
and (b) verbal and nonverbal communication, with (c)
restricted and repetitive behaviors or interests (APA,
1994). There is, nonetheless, marked variability in the
severity of symptomatology across patients, and level of
intellectual function can range from profound mental re-
tardation through the superior range on conventional IQ
tests. The DSM-IV criteria for Autistic Disorder are pre-
sented in Table II and are described below for each
neurobehavioral domain. The symptoms and signs rep-
resent a summary of clinical features which are discussed
in greater detail in the DSM-IV (APA, 1994), in the
monograph edited by Rapin (1996c), in the Wing Autis-
tic Disorders Interview Checklist- Revised (Wing, 1996),
and in numerous additional publications describing the
clinical presentation of the Autistic Spectrum Disorders
(Allen, 1991; Bauman, Filipek, & Kemper, 1997; D. J.
Cohen & Volkmar, 1997; Filipek, 1999; Lord & Paul,
1997; Minshew, 1996a; Rapin, 1997).
(DSM-IV A1). Qualitative Impairment in Social
It is important to understand that these criteria refer
to a qualitative impairment in reciprocal social interac-
tions, and not to the absolute lack of social behaviors.
The behaviors under this rubric range from total lack of
awareness of another person, to eye contact which is
present but not used to modulate social interactions. The
outline for this section follows the DSM-IV outline for
the criteria for Autistic Disorder (Table II) (APA, 1994).
Table II. Diagnostic Criteria for 299.00 Autistic Disorder
A. A total of six (or more) items from (1), (2), and (3), with two
from (1), and at least one each from (2) and (3):
(1) qualitative impairment in social interaction, manifest by at
least two of the following:
a) marked impairment in the use of multiple nonverbal
behaviors, such as eye-to-eye gaze, facial expression,
body postures, and gestures, to regulate social interac-
b) failure to develop peer relationships appropriate to
c) a lack of spontaneous seeking to share enjoyment, inter-
ests, or achievements with other people (e.g., by lack of
showing, bringing or pointing out objects of interest);
d) lack of social or emotional reciprocity
(2) qualitative impairment in communication, as manifest by at
least one of the following:
a) delay in, or total lack of, the development of spoken
language (not accompanied by an attempt to compen-
sate through alternative modes of communication such
as gesture or mime);
b) in individuals with adequate speech, marked impairment
in the ability to initiate or sustain a conversation with
c) stereotyped and repetitive use of language, or idiosyn-
d) lack of varied, spontaneous make-believe, or social imi-
tative play appropriate to developmental level.
(3) restrictive repetitive and stereotypic patterns of behavior,
interests, and activities, as manifested by at least one of
a) encompassing preoccupation with one or more stereo-
typed and restricted patterns of interest that is abnormal
either in intensity or focus;
b) apparently inflexible adherence to specific nonfunc-
tional routines or rituals;
c) stereotyped and repetitive motor mannerisms (e.g., hand
or finger flapping or twisting, or complex whole-body
d) persistent preoccupation with parts of objects.
B. Delays or abnormal functioning in at least one of the following
areas, with onset prior to age 3 years: (1) social interaction,
(2) language as used in social communication, or (3) symbolic
or imaginative play.
C. The disturbance is not better accounted for by Rett's Disorder
or Childhood Disintegrative Disorder.
° Reprinted with permission from the Diagnostic and Statistical
Manual of Mental Disorders (4th ed., pp. 70-71 Washington, DC:
American Psychiatric Association, 1994.
Filipek et al.
(Ala). Marked Impairment in the Use of Multiple
Nonverbal Behaviors, Such As Eye-to-Eye Gaze, Fa-
cial Expression, Body Posture, and Gestures to Regu-
late Social Interaction. As infants, some children with
autism do not lift up their arms or change posture in an-
ticipation of being held. They may not or may cuddle or
stiffen when held, and often do not look or smile when
making a social approach. Some children do make eye
contact, often only in brief glances, but the eye contact
is usually not used to direct attention to objects or events
of interest. Other children make inappropriate eye con-
tact, by turning someone else's head to gaze into their
eyes. Autistic children often ignore a familiar or unfa-
miliar person because of a lack of social interest. Some
children do make social approaches, although their con-
versational turn-taking or modulation of eye contact is
often grossly impaired. At the opposite extreme of so-
cial interactions, some children may make indiscrimi-
nate approaches to strangers (e.g., may climb into the
examiner's lap before the parent has even entered the
room, be unaware of psychological barriers, or be de-
scribed as a child who continuously and inappropriately
"gets into your face" in an intrusive manner).
(Alb). Failure to Develop Peer Relationships Ap-
propriate to Developmental Level. Younger children may
demonstrate lack of interest, or even apparent lack of
awareness of peers or other children. Some children with
autism have no age-appropriate friends, and often older
children may be teased or bullied. A child may want
"friends" but usually does not understand the concept of
the reciprocity and sharing of interests and ideas inher-
ent in friendship. For example, they might refer to all
classmates as "friends." One telling example is the child
who said without compunction, "Oh, I have many, many,
twenty-nine friends, but none of them like me." Verbal
children may have one "friend" but the relationship may
be very limited or may focus only on a similar circum-
scribed interest, such as a particular computer game.
Often, children gravitate to adults or to older peers, in
which case they play the role of a follower, or to much
younger peers, where they become the director. In either
case, the demands on social reciprocity are much less
compared to interactions with age-appropriate peers.
(A1c). A Lack of Spontaneous Seeking to Share En-
joyment, Interests, or Achievements with Other People
(e.g., by a Lack of Showing, Bringing, or Pointing Out
Objects of Interest). As infants, some children with
autism do not reciprocate in lap play, but rather either
hold the parent's arms as the parent performs the game
in a mechanical fashion, or insist that the parent watch
the child perform the game. Regardless, the character-
istic give-and-take in lap play that is seen in typically
developing children by the end of the first year is often
missing. They often do not point things out or use eye
contact to share the pleasure of seeing something with
another person, which is called joint attention.
(A1d). Lack of Social or Emotional Reciprocity.
Some children with autism show no interest in other chil-
dren or adults, and tend to play alone by themselves away
from others. Others play with adults nearby, or sit on the
outskirts of other children's play and either engage in
parallel play or simply watch the other children. Some
children involve other children in designated, often
repetitive play, but often only as "assistants" without
heeding any suggestions from the other children. Some
tend to serve in the passive role in other children's play,
for example as the baby in a game of "house," and sim-
ply follow others' directions. Other children may seek
out one specific child with whom there is a limited soli-
tary interest that dominates the entire relationship.
(A2). Qualitative Impairment in Communication
The communication impairments seen in the autis-
tic spectrum are far more complex than presumed by
simple speech delay and share some similarities with
the deficits seen in children with developmental lan-
guage disorders or specific language impairments
(Allen & Rapin, 1992). Expressive language function
across the autistic spectrum ranges from complete
mutism to verbal fluency, although fluency is often ac-
companied by many semantic (word meaning) and ver-
bal pragmatic (use of language to communicate) errors.
Young autistic children, even if verbal, almost univer-
sally have comprehension deficits, in particular deficits
in understanding higher order complex questions.
Deficits in pragmatics, the use of language to commu-
nicate effectively, are also almost universally present.
Some children with autism do not respond to their
names when called by a parent or other favored care-
taker, and often they are initially presumed to be se-
verely hearing-impaired. This syndrome, verbal audi-
tory agnosia (VAA), is similar to adult-onset acquired
word deafness, with one very important exception:
adults with acquired word deafness remain fluent be-
cause their language has been overlearned, whereas
children with autism with either developmental VAA
or acquired VAA with an epileptiform aphasia usually
are mute (Rapin & Allen, 1987).
(A2a). Delay in, or Total Lack of, the Development
of Spoken Language (Not Accompanied by an Attempt
to Compensate Through Alternative Modes of Com-
munication Such As Gesture or Mime). In early infancy,
some children with autism do not babble or use any
Screening and Diagnosis of Autistic Spectrum Disorders
other communicative vocalizations, and are described
as very quiet babies. Some children have absolutely no
spoken language when speech should be developing,
and also fail to compensate with facial expressions or
gestures. A typically developing infant or toddler may
pull his mother over to a desired object, but then will
clearly point to the object while looking at the mother's
face. In contrast, a characteristic behavior of many chil-
dren with autism is to mechanically use another per-
son's hand to indicate the desired object, often called
"hand over hand pointing." Some children even throw
another's arm up towards the desired object that is out
of reach, without any communicative pointing, gestur-
ing, or vocalizations. Other "independent" children
make no demands or requests of the parents, but rather
learn to climb at a young age and acquire the desired
object for themselves.
(A2b). In Individuals with Adequate Speech,
Marked Impairment in the Ability to Initiate or Sustain
a Conversation with Others. Some children with autism
speak relatively fluently, but are unable to engage in a
conversation, defined as two or more parties communi-
cating in a give-and-take fashion on a mutually agreed
upon topic. In a conversation, Partner A makes a state-
ment in turn on the given topic that is directed at Part-
ner B, who then makes another statement directed back
at Partner A, which is continued over more than one
cycle of turn-taking. Questions may be included, but they
are obviously not the dominant sentence structure used
in conversation. A hallmark of verbally fluent autistic
children is their inability to initiate or sustain a conver-
sation on a topic of mutual interest, although they may
be able to respond relatively well to, or ask a myriad of
questions, or talk "at" another person in a monologue or
soliloquy about their favorite topic.
(A2c). Stereotyped and Repetitive Use of Language,
or Idiosyncratic Language. A hallmark of autistic speech
is immediate or delayed echolalia. Immediate echolalia
refers to immediate repetition of words or phrases spo-
ken by another—the children are simply repeating ex-
actly what was heard without formulating their own lan-
guage. It is important to realize that immediate echolalia
is a very crucial aspect of normal language development
in infants under the age of 2 years. It becomes patho-
logic when it is still present as the sole and predominant
expressive language after the age of about 24 months,
and can often be present throughout the preschool or
school-age years in children with autism. It is impera-
tive to differentiate speech that consists predominantly
of immediate echolalia from the more classic picture of
immediate echolalia progressing rapidly to spontaneous
phrase speech in typically developing toddlers. Delayed
echolalia or scripts refer to the use of ritualized phrases
that have been memorized (e.g., from videos, television,
commercials, or prior overheard conversations). The ori-
gin of this stereotypic language does not necessarily have
to be clearly identifiable. Many older children with
autism incorporate the scripts in appropriate conversa-
tional context, which can give much of their speech a
"rehearsed" and often more fluent quality relative to the
rest of their spoken language. Children also show diffi-
culties with pronouns or other words that change in
meaning with context, and often reverse pronouns or
refer to themselves in the third person or by name.
Others may use literal idiosyncratic phrases or neolo-
gisms. Verbal children with autism may speak in very
detailed and grammatically correct phrases, which are
nonetheless repetitive, concrete, and pedantic. If a child's
answers to questions seem to "miss the point," further
history and conversation should be elicited with the
child, as this is also a hallmark of autistic language
deficits. These children typically answer factual ques-
tions correctly and appropriately, but when asked a ques-
tion that requires understanding concepts or concept for-
mation, they give details that are often only tangentially
related to the actual question.
(A2d). Lack of Varied, Spontaneous Make-Believe,
or Social Imitative Play Appropriate to Developmental
Level. Some children with autism do not use miniature
objects, animals, or dolls appropriately in pretend play.
Others use the miniatures in a repetitive mechanical
fashion without evidence of flexible representational
play. Some highly verbal children may invent a fantasy
world which becomes the sole focus of repetitive play.
A classic example of the lack of appropriate play is the
verbal autistic preschooler who "plays" by repeatedly
reciting a soliloquy of the old witch scene verbatim from
Beauty and the Beast while manipulating dollhouse
characters in sequence precisely according to the script.
When given the same miniature figures and dollhouse,
but instructed to play something other than Beauty and
the Beast, this same child is incapable of creating any
other play scenario.
(A3). Restricted, Repetitive, and Stereotypic Patterns
of Behaviors, Interests, and Activities
Again, this category of stereotyped behaviors and
interests, like the previous ones, encompasses qualitative
deficits in several behaviors.
(A3a). Encompassing Preoccupation with One or
More Stereotypic and Restricted Patterns of Interest
That Is Abnormal in Intensity or Focus. Some verbal
children with autism ask the same question repeatedly,
regardless of what reply is given, or engage in highly
Filipek et al.
repetitive perseverative play. Others are preoccupied
with unusual special interests. For example, many chil-
dren are fascinated with dinosaurs, but children with
autism may not only amass exhaustive facts about every
conceivable type of dinosaur, but also about which mu-
seums house which particular fossils, and so forth; these
children will often repeatedly "share" their knowledge
with others regardless of the others' interest or sugges-
tions to the contrary. Some autistic preschoolers are
zealous fans of Wheel of Fortune or Jeopardy, even
when still preverbal or minimally verbal; this unusual
interest in a preschool child is considered by many to
be a hallmark of autism (Allen, 1991).
(A3b). Apparently Inflexible Adherence to Specific
Nonfunctional Routines or Rituals. Many children with
autism are so preoccupied with "sameness" in their
home and school environments or with routines, that lit-
tle can be changed without prompting a tantrum or other
emotional disturbance. Some may, for example, insist
that all home furnishings remain in the same position,
or that all clothing be of a particular color, or that only
one specific set of favored sheets be on the bed. Others
may eat only from a specific plate when sitting in a spe-
cific chair in a specific room, which may not necessar-
ily be the kitchen or dining room. Some children may
insist on being naked while in the home, but insist on
wearing shoes to the dinner table. This inflexibility may
also extend to familiar routines, for example, taking only
a certain route to school, or entering the grocery store
only by one specific door, or never stopping or turning
around once the car starts moving. Many parents may
either not be aware that they are following certain ritu-
als to avoid an emotional upheaval, or may be aware
but too embarrassed to volunteer such information.
Within this context, some children have distinct behav-
ioral repertoires that they self-impose to sustain same-
ness, even when not imposed externally. By adulthood,
many of these rituals may evolve to more classic
obsessive-compulsive symptoms, including hoarding
unusable or broken objects, or repetitively whispering
words or phrases to themselves.
(A3c). Stereotyped and Repetitive Motor Manner-
isms (e.g., Hand or Finger Flapping or Twisting or
Complex Whole-Body Movements). Some children will
have obvious stereotypic motor movements, such as
hand clapping or arm flapping whenever excited or
upset, which is pathologic if it occurs after the age of
about 2 years. Running aimlessly, rocking, spinning,
bruxism, toe-walking, or other odd postures are com-
monly seen in children with autism. Others may simply
repetitively tap the back of their hand in a less obtru-
sive manner. It has been noted that, in higher function-
ing youngsters, the stereotypic movements may become
"miniaturized" as they get older into more socially ac-
ceptable behaviors, such as pill-rolling (Bauman, 1992a;
Rapin, 1996c). It is also important to realize that not all
children with autism have repetitive motor movements.
(A3d). Persistent Preoccupation with Parts of
Objects. Many children demonstrate the classic behav-
ior of lining up their toys, videotapes, or other favored
objects, but others may simply collect "things" for no
apparent purpose. Many engage in repetitive actions,
such as opening and closing doors, drawers, or flip-top
trash cans, or turning light switches off and on. Others
are fascinated and repetitively flick strings, elastic
bands, measuring tapes, or electric cords. Younger chil-
dren with autism are often particularly fascinated with
water, and they especially enjoy transferring water
repetitively from one vessel into another. Some may
taste or smell items. Others love spinning objects, and
may either spend long periods spinning the wheels of
a toy car or watching ceiling fans, or spinning them-
selves until they fall from dizziness. Some children will
often look at objects out of the corner of their eyes.
Unbeknownst to each other, the year after Kanner's
(1943) first description of autism, a pediatrician named
Asperger (1991/1944) also described four children with
"autistic psychopathy," who had presumably milder
autistic behaviors and normal IQ. This report written in
German was not widely known until the 1980s (Wing,
1981b). The diagnostic term was included for the first
time in DSM-IV (APA, 1994), and the criteria for the
qualitative impairments in social interaction, and re-
strictive and repetitive patterns of behaviors and activi-
ties are identical to those for Autistic Disorder. This di-
agnostic category is clearly in evolution and, as discussed
in Schopler, Mesibov, and Kunce (1998), it is unclear
whether it will remain a valid syndrome separate from
In contrast to the Autistic Disorder criteria which
include deficits in verbal and nonverbal communication
and play, Asperger criteria currently state that there is no
evidence of "clinically significant" language delay, such
that the child used single words by age 2 years, and com-
municative phrases by age 3 years (APA, 1994). (Note
that these criteria for language delay are much laxer than
those recommended for referral in the current guidelines.)
Normal or near-normal IQ is also the rule, including self-
help skills, "adaptive behavior (other than in social in-
teraction), and curiosity about the environment in child-
hood." The lack of clear language deviance usually leads
Screening and Diagnosis of Autistic Spectrum Disorders
to later clinical recognition than with other autistic spec-
trum disorders, which is presumably due to the normal
or near-normal adaptive behavior early in life (Volkmar
& Cohen, 1991). Yet, the language in Asperger's is
clearly not typical or normal. Individuals with Asperger
disorder usually have pedantic and poorly modulated
speech, poor nonverbal pragmatic or communication
skills, and intense preoccupations with circumscribed top-
ics such as the weather or railway timetables (Ghaziud-
din & Gerstein, 1996; Klin, Volkmar, Sparrow, Cicchetti,
& Rourke, 1995; Wing, 198l a). Their speech is often
concrete and literal, and their answers often "miss the
point." Some clinicians have mislabeled individuals with
this speech pattern as having a Semantic-Pragmatic Lan-
guage Disorder rather than Asperger's or autism (Bishop,
Hartley, & Weir, 1994; Bishop, 1989; Gagnon, Mottron,
& Joanette, 1997). However, this diagnosis of a language
disorder is not an appropriate substitution for the diag-
nosis of autism, as it does not account for the social
deficits and restrictive, repetitive interests.
Socially, individuals with Asperger disorder are
usually unable to form friendships. Because of their
naive, inappropriate one-sided social interactions, they
are also often ridiculed by their peers. Often they cease
their attempts because of the cruel ridicule, and remain
extremely socially isolated. Yet, they honestly desire
success in interpersonal relationships, and are often quite
puzzled when they do not succeed (Bonnet & Gao,
1996). They often have both fine and gross motor
deficits, including clumsy and uncoordinated movements
and odd postures (Asperger, 1991/1944; Klin et al.,
1995; Wing, 1981a). However, motor apraxia is an in-
consistent finding, as formal tests of motor abilities do
not differentiate high-functioning autism from Asperger
disorder (Ghaziuddin, Butler, Tsai, & Ghaziuddin, 1994;
Manjiviona & Prior, 1995).
The validity of Asperger disorder as a discrete di-
agnostic entity distinct from high-functioning (verbal)
autism remains controversial (Kurita, 1997; Schopler,
1996; Schopler et al., 1998; Volkmar et al., 1996). Clin-
ically, the diagnosis of Asperger disorder is often given
as an alternative, more acceptable, "A-word" to high-
functioning children with autism (Bishop, 1989). There
are multiple partially overlapping clinical criteria cur-
rently in use around the world for the diagnosis of As-
perger disorder, which adds to the confusion (APA, 1994;
Attwood, 1998; Gillberg & Gillberg, 1989; 1995; Szat-
mari, Bremner, & Nagy, 1989; Wing, 1981a; WHO,
1992, 1993). The similarity and overlap of signs and
symptoms of Asperger's with the Syndrome of Nonver-
bal Learning Disabilities further expands the spectrum
of these developmental disorders (Harnadek & Rourke,
1994; Klin et al., 1995; Rourke, 1989a, 1989b; Voeller,
1986). However, again, a diagnosis of a learning dis-
ability is not an appropriate substitution for a diagnosis
of autism, as all too often it does not account for the
social deficits and restrictive, repetitive interests. To add
to the confusion, a recent retrospective review of the orig-
inal four Asperger cases (1991/1944) reported that these
children actually meet current DSM-IV (APA 1994) cri-
teria for Autistic Disorder (Miller & Ozonoff, 1997). As
DSM-IV is now written, if criteria for Autistic Disorder
are met, this precludes a diagnosis of Asperger disorder.
Childhood Disintegrative Disorder
Childhood Disintegrative Disorder (CDD) refers to
the rare occurrence of normal early development until at
least age 24 months, followed by a rapid neurodevelop-
mental regression that results most often in autistic symp-
tomatology. CDD, previously called Heller's syndrome,
dementia infantilis or disintegrative psychosis, usually
occurs between 36 and 48 months of age but may occur
up to 10 years of age. There have been only a hundred
or so reports of CDD in the literature (Volkmar, Klin,
Marans, & Cohen, 1997; Volkmar & Rutter, 1995). The
hallmark signs include the loss of previously normal lan-
guage, social, play, or motor skills, and frequently in-
clude the onset of restrictive repetitive behaviors, all typ-
ical of autism (APA, 1994). CDD is usually associated
with more severe autistic symptoms than is early-onset
autism, including profound loss of cognitive skills re-
sulting in mental retardation (Catalano, 1998; Evans-
Jones & Rosenbloom, 1978; Hoshino et al., 1987; Short
& Schopler, 1988; Tuchman & Rapin, 1997; Volkmar &
Rutter, 1995). A recent review of CDD noted a 4:1 male
predominance, mean age of onset of 29 ± 16 months,
with over 95% showing symptoms of speech loss, social
disturbances, stereotyped behaviors, resistance to change,
anxiety and deterioration of self-help skills (Volkmar,
In children with autism, it is also well recognized
that clinical regression can and often does occur as early
as 15 months of age, with a mean age of 21 months
(Tuchman, 1996). The relationship between autism with
an early regressive course (before 36 months), CDD
(after 36 months), Landau-Kleffner syndrome (Landau
& Kleffner, 1957; Landau & Kleffner, 1998), and elec-
trical status epilepticus during slow wave sleep (ESES)
is currently poorly understood, as is the underlying eti-
ology and pathophysiology (Bristol et al., 1996; Tuch-
man & Rapin, 1997). Estimates of the rates of regres-
sion in children with autism range from 10 to over 50%
(Hoshino et al., 1987; Tuchman & Rapin, 1997), with
Filipek et al.
total loss of expressive language occurring in between
20 and 40% (Kurita, 1985,1996; Kurita, Kita, & Miyake,
1992; Rutter & Lord, 1987). Between 36 and 55% of
parents of children with autism note problems in the first
year of life, but likely only retrospectively (Short &
Schopler, 1988; Volkmar, Stier, & Cohen, 1985). Some
children had autistic symptoms quite early, but did not
receive a medical referral or assessment until 2 or 3 years
of age. Either parents failed to recognize the insidious
problems or the physician or others discounted the
parental concerns. Acute or subacute loss of language is
more likely to motivate parents to seek medical help than
is the onset of social abnormalities (Rogers & DiLalla,
1990). One of the most troubling problems hindering a
better understanding of autistic regression and CDD in-
volves the disentangling of "age at onset" from "age at
recognition" (Volkmar et al., 1985). Retrospective eval-
uation of home movies and videotapes is now a well-
accepted research strategy for identifying autistic symp-
toms by as early as 12 months of age (Adrien et al., 1992;
Baranek, 1999; Osterling & Dawson, 1994).
Autism with regression and CDD have both been
associated with seizures or epileptiform electroencepha-
lograms (EEG) (Rapin, 1997; Tuchman, 1995; Tuchman
& Rapin, 1997; Tuchman, Rapin, & Shinnar, 1991a,
1991b). In a recent study of children with autism with a
history of regression (Tuchman & Rapin, 1997), there
were almost twice as many children in the sample with
epileptiform EEGs (21%) as there were with clinical
epilepsy (11%), which indexes a significant portion of
children with autism with subclinical epileptiform ac-
tivity. These investigators suggested that regression has
a significant association with an epileptiform EEG, even
in the face of a lack of clinical seizure activity (19% in
those with regression vs. 10% in those without). The ma-
jority of the epileptiform EEGs were localized to the
centrotemporal regions. It is noteworthy that seizures
or epileptiform EEGs were more prevalent in those chil-
dren with regression who also demonstrated a significant
cognitive deficit (Tuchman & Rapin, 1997).
Atypical Autism/ PDD Not Otherwise
These diagnoses are used when clinically signifi-
cant autistic symptomatology is present, including
deficits in reciprocal social interactions, verbal or non-
verbal communication, or stereotyped behavior, inter-
ests, and activities, but full criteria are not met for an al-
ternative specific diagnosis under the autistic spectrum
or PDD umbrella; for example, in a child who does not
meet the required total of 6 of the possible 12 criteria
for the diagnosis of Autistic Disorder, or who had symp-
tom onset after age 36 months. Also, children whose
symptoms are atypical or not as severe would be coded
under this diagnosis (APA, 1994).
Atypical autism/ PDDNOS is not a distinct clinical
entity with a specific definition, although individuals
given this diagnosis are traditionally thought to have
milder symptoms. PDDNOS is a diagnosis by exclusion
of the other autistic spectrum disorders (Towbin, 1997).
It is often used as a "default" or "wastebasket" diagno-
sis when either insufficient or unreliable information is
available, or when the practitioner is hesitant to use the
term "autism." Indeed, when 176 children diagnosed by
DSM-III-R criteria (APA, 1987) with Autistic Disorder
were compared with 18 children diagnosed with
PDDNOS, no significant differences were noted on any
neuropsychological or behavioral measures when co-
varied for nonverbal IQ (Rapin et al., 1996). Screening
and diagnostic procedures for atypical autism/PDDNOS
is the same as for the other autistic spectrum disorders,
as is management.
Rett syndrome, a neurodegenerative disorder es-
sentially limited to girls, becomes manifest after a pe-
riod of normal function after birth. Although it was first
described by Rett in 1966, clinical awareness of the syn-
drome did not occur until Hagberg et al. (1983) reported
35 additional cases. The girl with Rett syndrome initially
presents as early as age 6 to 8 months, after a normal
birth, a normal newborn head circumference, and nor-
mal early developmental milestones, with a decelerating
head circumference growth rate. This is eventually fol-
lowed by microcephaly (i.e., head circumference less
than the second percentile) and by the loss of purpose-
ful hand skills. Subsequently, stereotypic hand move-
ments such as wringing, washing, licking, or clapping,
and poor truncal or gait coordination develop, with loss
of social engagement and severely impaired receptive
and expressive language development and cognitive
skills (Armstrong, 1997; Hagberg et al., 1983; Naidu,
1997; Percy, Gillberg, Hagberg, & Witt-Engerstrom,
1990). Almost all the children have abnormal EEGs with
slow background activity and spikes, but clinical seizures
occur in only about one third of cases (Armstrong, 1997;
Naidu, 1997; Percy et al., 1990). There is general agree-
ment that Rett syndrome is a developmental disorder, al-
though its classification in DSM-IV and ICD-10 as a
PDD remains controversial (Burd, Fisher, & Kerbeshian,
1989; Gillberg, 1994; Tsai, 1992). However, it was clas-
sified under the PDD umbrella so that a misdiagnosis of
Screening and Diagnosis of Autistic Spectrum Disorders
autism would not be given in lieu of the correct diag-
nosis of Rett syndrome.
SCREENING AND DIAGNOSIS OF AUTISM:
"SCREEN, PROBE, EVALUATE"
Screening for autism calls for two different levels
of investigation, each answering a different question
(Siegel, 1998). Level 1 screening should be performed
on all children and involves identifying children at risk
for any type of atypical development. Level 2 involves
a more in-depth investigation of children already iden-
tified to be at risk for a developmental disorder, differ-
entiates autism from other kinds of developmental dif-
ficulties, and includes evaluations by autism specialists
aimed at determining the best means of intervention
based on the child's profile of strengths and weaknesses.
Please refer to the Algorithm (Fig. 1) for an overview of
this process. Although the process itself has been sepa-
rated into two levels of evaluation, this does not neces-
sarily indicate separate independent levels of profes-
Fig. 1. Algorithm.
sional involvement, as a given single professional may
well perform both sequential stages.
Since we currently have no biological marker for
autism, screening must focus on behavior. Furthermore,
in most cases, autism appears to have a gradual onset,
often without clear evidence of sensorimotor impair-
ment. Children with autism typically sit, crawl, and
walk at the expected age. Many even produce a few
words at developmentally appropriate times, although
these words seldom develop into useful early language.
Symptoms that may be present during infancy (a seri-
ous expression, increased irritability, sleep and eating
difficulties, and placidity) are behaviors commonly
seen in otherwise typically developing children.
At the present time, specific behaviors that distin-
guish infants with autism from others at 12 months of
age have been identified in studies using observations
based on home videotapes (Osterling & Dawson, 1994).
Using home videotapes of first birthday parties in infants
with autism versus typical development, these investi-
gators found that four behaviors correctly identified over
90% of the autistic and typical infants. These behaviors,
which were replicated in a subsequent study (Mars,
Mauk, & Dowrick, 1998), were eye contact, orienting to
name being called, pointing, and showing. A more recent
study of home videotapes of first birthdays (Osterling &
Dawson, 1999) found that these 1-year-olds with autism
could also be distinguished from 1-year-olds with idio-
pathic mental retardation. One-year-old infants with
autism used less eye contact and oriented to their names
less frequently than those with mental retardation and
those with typical development. Furthermore, these same
behaviors distinguished these same infants with autism
at 8 to 10 months from those with typical development
(Brown, Dawson, Osterling, & Dinno, 1998). Baranek
(1999) similarly used retrospective video analysis with
9- to 12-month-old infants and found that a pattern of
nine behaviors differentiated between autism, develop-
mental disabilities and typical development with 94% ac-
curacy. The autistic pattern included greater problems
with responsiveness to social stimuli (e.g., delayed re-
sponding to name; social touch aversion) as well as other
nonsocial aspects of sensory responsiveness. Although
the long-range stability and predictive utility of these
findings remains to be determined, these results suggest
that autism will eventually be reliably detected as early
as 1 year of age, or even younger (Baranek, 1999; Teit-
elbaum, Teitelbaum, Nye, Fryman, & Maurer, 1998).
Autism can be diagnosed reliably in children by
or before the age of 3 years. Recent studies have demon-
strated that symptoms of autism are measurable by
18 months of age, and that these symptoms are stable
Filipek et al.
from toddler age through the preschool age (Charman
et al., 1997; Cox et al., 1999; Lord, 1995; Stone et al.,
1999). Furthermore, these studies have identified the main
characteristics that differentiate autism from other de-
velopmental disorders in the 20-month to 36-month age
range, characteristics that early screening tools need to
target. These involve negative symptoms, or behavioral
deficits, in the following areas: eye contact, orienting to
one's name, joint attention behaviors (e.g., pointing,
showing), pretend play, imitation, nonverbal communi-
cation, and language development. There is some indi-
cation that socially directed emotional behavior may also
differentiate the groups; neither sensory-perceptual nor
positive symptoms such as repetitive behaviors or be-
havioral outbursts appear to consistently differentiate
between autistic and nonautistic groups early on.
Screening for autism may not identify children with
milder variants of the disorder (without mental retarda-
tion or obvious language delay). These children's diffi-
culties often go undiagnosed for years, causing them in-
creasing difficulty as they try to meet the demands of
elementary education without needed supports. Their dif-
ficulties cause great stress for their families, who recog-
nize the child's challenges but have difficulty convinc-
ing others that their child has a disability. These children
and their families will benefit greatly from improved
screening efforts and the increased opportunity for ef-
fective intervention that screening activities can yield.
However, this screening also needs to target the symp-
toms of verbal individuals with high-functioning autism
and Asperger disorder, and must focus on older children,
adolescents, and young adults (Garnett & Attwood,
1998). Such screens are also relevant for educational set-
tings, where these older children may also be recognized.
Level 1: Routine Developmental Surveillance
and Screening Specifically for Autism
It is the consensus of this Panel that primary care
providers must change their approach to well-child care,
so as to perform proactive screening for developmental
disorders. It has been estimated that almost 25% of chil-
dren in any practice demonstrate developmental issues
at some point. Therefore, developmental screening must
become an absolutely essential routine of each and every
well-child visit throughout infancy, toddler, and pre-
school years, and even beyond early school-age if con-
cerns are raised. The additional use of Specific Devel-
opmental Probes will increase the sensitivity and
specificity of the screening process for autism.
Unfortunately, fewer than 30% of primary care
providers conduct standardized screening tests (in the
rigid manner for which they were intended) at well-
child appointments (Dworkin, 1989, 1992; Majnemer &
Rosenblatt, 1994; Rapin, 1995). Additionally, the Amer-
ican Academy of Pediatrics (AAP) is stressing the im-
portance of developmental surveillance at every well-
child visit: a flexible, continuous process that is broader
than screening and includes eliciting and valuing parental
concerns, specific probing regarding age-appropriate
skills in each developmental domain, and skilled obser-
vations (American Academy of Pediatrics Committee on
Children with Disabilities, 1994; Johnson & Blasco,
1997). Implementation of the developmental surveillance
process at every well-child visit and the acquisition
of the necessary skills to make it happen will only be
accomplished with training at the preservice and in-
service levels. Additionally, current managed-care pol-
icy, which allows only a few minutes for well-child ap-
pointments, must change if clinicians are to implement
the training they receive (Glascoe, Foster, & Wolraich,
1997). A high degree of advocacy on the part of parents,
health care professionals, and managed care adminis-
trators is essential if the recommendations of this Prac-
tice Parameter are to be appropriately implemented.
It is important to realize that parents usually are cor-
rect in their concerns about their child's development
(Glascoe, 1994, 1997, 1998; Glascoe & Dworkin, 1995).
They may not be as accurate regarding the qualitative and
quantitative parameters surrounding the developmental
abnormality, but almost always, if there is a concern,
there is indeed a problem in some aspect of the child's
development. Any developmental concern on Chief Com-
plaint must be valued and lead to further investigation.
Although a positive parental concern strongly sug-
gests an underlying developmental problem, the lack
of concern does not imply normal development. Lack
of parenting experience, cultural influences, denial,
time constraints in the presence of more pressing med-
ical issues, all contribute to parental reluctance to bring
up developmental issues. Even when the parents ex-
press no concerns, a child's development should be
monitored closely by using one of the available parental
questionnaire instruments. Some clinics utilize well-
child clinic forms with preprinted developmental mile-
stones that are appropriate for each routine visit. The
information on these forms should be taken from valid
milestone charts and cover each developmental domain.
General Developmental Screening: Parental
Traditional Instruments. The Denver-II (DDST-II,
formerly the Denver Developmental Screening Test-
Screening and Diagnosis of Autistic Spectrum Disorders
Revised; Frankenburg, Dodds, Archer, Shapiro, & Bres-
nick, 1992) has been the traditional tool used for devel-
opmental screening in primary care practices. It is de-
signed for children from birth to 6 years of age, and
samples receptive and expressive language, articulation,
fine motor-adaptive, personal-social, and gross motor
skills. It yields a single score (abnormal, questionable,
untestable, normal, or advanced). Easy to administer and
score, the test can be completed in 25 minutes or less.
However, the validity of the test has not been studied. In
addition, subsequent research found that the measure was
significantly insensitive (meaning that the instrument
missed a significant number of delayed children—many
missed true positives) and lacked specificity (meaning
that a significant number of normal children—true neg-
atives—were misclassified as delayed) (Glascoe et al.,
1992). The Revised Denver Pre-Screening Developmen-
tal Questionnaire (R-DPDQ; Frankenburg, 1986), in con-
trast, is designed to identify a subset of children who
need further screening. It uses parental report and pres-
ents 10 to 15 items, sampling the various domains, in the
age range of birth to 6 years. R-DPDQ items were drawn
from the Denver Developmental Screening Test (the very
popular predecessor of the Denver-II) which detected
only 30% of children with language impairments and
50% of children with mental retardation (Borowitz &
Glascoe, 1986; Glascoe et al., 1992; Greer, Bauchner, &
Zuckerman, 1989). Many other comprehensive studies
also document the lack of sensitivity and specificity of
this instrument (Cadman et al., 1984; Camp, van Doorn-
inck, Frankenburg, & Lampe, 1977; Diamond, 1987;
Grant & Gittelsohn, 1972; Harper & Wacker, 1983;
Lindquist, 1982; Sciarillo, Brown, Robinson, Bennett,
& Sells, 1986; Sturner, Green, & Funk, 1985). Because
of the lack of sensitivity and specificity of both the
DDST-II and R-DPDQ, an alternative instrument must
be used for appropriate Level 1 primary-care screening
at every well-child visit.
Standardized Developmental Screening Instru-
ments. Examples of Level 1 parent questionnaires with
acceptable psychometric properties include: (a) The Ages
and Stages Questionnaire, Second Edition (ASQ; Bricker
& Squires, 1994; Bricker & Squires, 1999; Squires,
Bricker, & Potter, 1997) uses parental report for children
from birth to 3 years, and provides clear drawings and
directions for eliciting thoughtful responses. Separate
forms of 10 to 15 items for each age range are tied to
the well-child visit schedule. Modifications are available
for screening children at other particular ages. Well-
standardized and validated, the ASQ has good sensitiv-
ity and excellent specificity and provides pass-fail scores.
Because it is difficult to use the single outcome score to
make referrals and because of the ASQ's brevity, it ap-
pears especially useful as a prescreening tool. (b) The
BRIGANCE® Screens (Brigance, 1986; Glascoe, 1996)
consist of seven separate forms, one for each 12-month
age range from 21 to 90 months of age. It taps key de-
velopmental and early academic skills, including speech-
language, fine and gross motor, graphomotor develop-
ment, and general knowledge at younger ages and also
reading and math at older ages. It uses direct elicitation
and observation, and takes in approximately 10 minutes
to administer. It is available in English or Spanish. It
is well standardized and validated, and has been in use
for over 10 years. The Screens produce cutoff and age-
equivalent scores for motor, language, and readiness, and
an overall cutoff score. The Screens also have good sen-
sitivity and specificity to giftedness. (c) The Child De-
velopment Inventories (CDIs; Ireton, 1992; Ireton &
Glascoe, 1995) include three separate measures with
60 items each (the Infant Development Inventory, birth
to 21 months of age; Early Child Development Inven-
tory, 15 to 36 months of age; and the Preschool Devel-
opment Inventory, 36 to 72 months of age). All are com-
pleted by parental report in about 5 to 10 minutes. The
CDIs can be self-administered in waiting or exam rooms
or mailed to families. For parents with limited English,
items can be directly administered to children. The CDIs
screen for language, motor, cognitive, preacademic,
social, self-help, behavior, and health problems. Forms
for the older two age groups produce a single cutoff score
equivalent to 1.5 standard deviations below the popula-
tion mean. Clinicians must then analyze errors to deter-
mine the domains in which children are having the most
difficulty in order to make appropriate referrals (e.g.,
fine motor deficits might dictate an occupational ther-
apy referral whereas global deficits dictate the need
for comprehensive assessment). Although the CDIs
were standardized exclusively in St. Paul, MN, a num-
ber of validity studies support the instruments' effec-
tiveness in other geographic locations, with minorities
and with groups with lower socioeconomic status (Chaf-
fee, Cunningham, Secord-Gilbat, Elbard, & Richards,
1990; Guerin & Gottfried, 1987; Ireton & Glascoe, 1995;
Sturner, Funk, Thomas, & Green, 1982). These also
showed the measures to have excellent sensitivity and
good specificity. The parent instrument to the CDIs, the
Child Development Inventory, is more of an assessment
than a screening tool for children 15 to 72 months of age.
(d) The Parents' Evaluation of Developmental Status
(PEDS, Glascoe, 1998) helps providers carefully elicit
and interpret parents' concerns. PEDS assigns probabil-
ities of delays and disabilities to the various types of con-
cerns, thus enabling clinicians to make evidence-based
Filipek et al.
decisions, provide in-office counseling, encourage sug-
gestions, and give reassurance. To use PEDS, parents
must answer 10 questions. These are written at the fifth-
grade level in English and in Spanish, and more than 90%
of parents can complete the questionnaire in writing
while they wait for their appointment. Clinicians or of-
fice staff can score and interpret the results in about 2
minutes. PEDS was validated and standardized on 971
children around the country in four separate validation
studies (Glascoe, 1991, 1994; Glascoe, Altemeier, &
MacLean, 1989; Glascoe, MacLean, & Stone, 1991). Its
accuracy in the detection of disabilities meets conven-
tional standards for screening tests (sensitivity to devel-
opmental problems and specificity to normal develop-
ment of 70 to 80%). Research on PEDS shows that
parents are likely to be accurate, regardless of their level
of education or parenting experience.
Chief Complaints and Specific Probes Regarding
There are at least three general concerns with
which young children and their parents present to the
primary care provider at a well-child visit: speech or
language delay; problems with social development with
or without similar concerns in speech or language; and
the development of a younger sibling of a child with
known or suspected autism. Any child whose parents
are concerned in these areas should be further evalu-
ated through Levels 1 and 2, as appropriate. Any con-
cern that implies "regression" or loss of skills in lan-
guage or social skills should be a serious red flag.
The Child Whose Parents Are Concerned about
Speech or Language Delay. Chief complaints about "iso-
lated" speech deficits are the most common concerns
raised by parents in children between the ages of 1 and
5 years. Most of the time these concerns relate to delayed
expressive language, because parents are not usually as
knowledgeable about their child's receptive language
skills. There are several classic parental concerns, as well
as absolute language milestone misses, either of which
should immediately prompt further investigation (Table
III). When these or other language concerns are voiced,
the Level 1 provider should probe with questions to the
parent regarding social skills and behavior, as well as
communication, in an effort to determine whether there
are any problems in addition to language (Table IV).
The Child with a Suspected Problem in Social De-
velopment or Behavior (with or without Similar Con-
cerns in Speech or Language). Any concerns regarding
problems with social development should always be
taken seriously, as seriously as an older child's com-
Table III. Parental Concerns that are RED FLAGS for Autism
Does not respond to his/her name
Cannot tell me what (s)he wants
Language is delayed
Doesn't follow directions
Appears deaf at times
Seems to hear sometimes but not others
Doesn't point or wave bye-bye
Used to say a few words, but now he doesn't
Doesn't smile socially
Seems to prefer to play alone
Gets things for himself
Is very independent
Does things "early"
Has poor eye contact
Is in his own world
Tunes us out
Is not interested in other children
Is hyperactive/uncooperative or oppositional
Doesn't know how to play with toys
Gets stuck on things over and over
Has unusual attachments to toys (e.g., always is holding a
Lines things up
Is oversensitive to certain textures or sounds
Has odd movement patterns
Absolute indications for immediate further evaluation
No babbling by 12 months
No gesturing (pointing, waving bye-bye, etc) by 12 months
No single words by 16 months
No 2- word spontaneous (not just echolalic) phrases by
ANY Loss of ANY Language or Social Skills at ANY Age
plaint of back or chest pain. Unlike "stomachaches" and
"headaches" which are common, self-limiting, and can
often be treated symptomatically without a diagnostic
workup, a complaint of back or chest pain is rare and
deserves investigation. Similarly, parents rarely com-
plain of social delays or problems, so any and all such
concerns should be immediately investigated. In addi-
tion, complaints about behavioral concerns that coexist
with any other concerns of social or communication de-
velopment should be immediately investigated (see Ta-
bles III and IV). It is even more significant when par-
ents voice additional concerns in the communication
and behavior areas as well as in socialization.
The Younger Sibling of an Older Child with
Known or Suspected Autism. The younger sibling(s) of
an autistic child deserves special attention whether or
Screening and Diagnosis of Autistic Spectrum Disorders
Table IV, Ask Specific Development Probes:
"Does (s)he . . ." or "Is there . . ."
. . . cuddle like other children?
. . . look at you when you are talking or playing?
. . . smile in response to a smile from others?
. . . engage in reciprocal, back-and-forth play?
. . . play simple imitation games, such as pat-a-cake or
. . . show interest in other children?
. . . point with his finger?
. . . gesture? nod yes and no?
. . . direct your attention by holding up objects for you to see?
. . . anything odd about his/her speech?
. . . show things to people?
. . . lead an adult by the hand?
. . . give inconsistent responses to name? . . . to commands?
. . . use rote, repetitive, or echolalic speech?
. . . memorize strings of words or scripts?
. . . have repetitive, stereotyped, or odd motor behavior?
. . . have preoccupations or a narrow range of interests?
. . . attend more to parts of objects (e.g., wheels)?
. . . have limited or absent pretend play?
. . . imitate other people's actions?
. . . play with toys in the same exact way each time?
. . . strongly attached to a specific unusual objects(s)?
not the parents have concerns about this child's de-
velopment. Siblings constitute an important autism-risk
group; their development needs to be monitored very
carefully not only for autism-related symptoms but also
for language delays and early anxiety symptoms. While
some parents may be overly vigilant regarding the pres-
ence of "autistic features" and overreact, other parents
may not realize that their younger child demonstrates
milder autistic symptoms, because the severity of the
older child overshadows the subtle abnormalities in the
younger. The main advantage of identifying young
children with autism as soon as possible is to provide
them with early treatment in high quality autism inter-
vention programs. Additionally, it is important to note
that a younger sibling may mimic their older autistic
sibling even when s/he has no innate autistic charac-
teristics of her/his own. When the parents do have a
concern, Level 1 screening should proceed directly to
the autism-specific questionnaires. When the parents
have no concerns, screening should both probe for
autistic behaviors and monitor all developmental do-
mains at each and every well-child visit. Because there
are no pathognomonic signs or diagnostic tests for
autism, the history is one of the most important tools
used to determine whether or not the child is at risk
for a diagnosis of autism. Level 1 professionals must
learn what questions to ask and how to interpret the
answers in the context of normal child development
(see Tables HI and IV).
Level 1 Laboratory Investigations
Formal Audiologic Evaluation
All children with developmental delays, especially
those with delays in social and language development,
should undergo a formal audiologic hearing evaluation.
This may become a moot point as the standard of pe-
diatric care moves toward universal screening. Until
such time, any child with delayed language or at risk
for autism should be provided with a referral for
audiologic testing on the same day that a concern is
Parent or practitioner concern regarding a speech,
language, or hearing problem (loss of sensitivity, incon-
sistent responses, no response, or unusual responses to
sounds or sound sources) should result in an immediate
referral for audiologic assessment. Comprehensive hear-
ing tests should be provided by an audiologist with ex-
perience in the assessment of very young children and
difficult-to-test populations. This referral should occur
regardless of the child having "passed" a neonatal hear-
ing screen. Integrity of hearing cannot be determined by
informal observations of behavioral responses to envi-
ronmental sounds or by parent-caregiver report. Hearing
loss (conductive, sensorineural, or mixed) can co-occur
with autism; children with autism may be incorrectly
thought to have peripheral hearing loss (Adkins & Ainsa,
1979; Jure, Rapin, & Tuchman, 1991; Klin, 1993; Smith,
Miller, Stewart, Walter, & McConnell, 1988). Audiologic
assessment should occur early in the differential diag-
nostic process and include a battery of tests including be-
havioral audiometric measures, assessment of middle-ear
function and electrophysiologic procedures (American
Speech-Language-Hearing Association, 1991).
The goal of audiologic assessment is to delineate
the type, degree, configuration, and symmetry of any
existing hearing loss or to confirm the presence of nor-
mal peripheral hearing sensitivity. Two broad categories
of hearing assessment methods are available: behavioral
and electrophysiologic. Behavioral audiologic assess-
ment should include measures of hearing that are ap-
propriate for the child's developmental level. Uncon-
ditioned behavioral response procedures (behavioral
observation audiometry or BOA) are of limited use in
characterizing hearing sensitivity as a function of fre-
quency. Conditioned response procedures (such as
Filipek et al.
Visual Reinforcement Audiometry or Conditioned Play
Audiometry) are useful in audiologic assessment of chil-
dren beginning at the developmental age of 6 months.
Reliable, accurate, frequency-specific threshold infor-
mation may be obtained using this simple, pleasant, and
cost-effective method. The audiologic assessment of chil-
dren with autism may present challenges for the audiol-
ogist requiring modifications of traditional test tech-
niques and test environments. Limited reports and
clinical experience suggest that many children with
autism may be assessed using operant test procedures
(Gravel, Kurtzberg, Stapells, Vaughan, & Wallace, 1989;
Verpoorten & Emmen, 1995).
Electrophysiologic procedures are useful for esti-
mating hearing sensitivity and for examining middle ear,
cochlear, and VII3Ith nerve or auditory brainstem path-
way integrity (Gorga, Kaminski, Beauchaine, Jesteadt,
& Neely, 1989; Stapells, Gravel, & Martin, 1995). These
methods require no behavioral response from the child,
although a child must be quiet (usually, in natural or se-
dated sleep) for varying amounts of time depending upon
the procedure. Acoustic immittance procedures, specif-
ically tympanometry, are useful for quantifying middle-
ear function, and acoustic reflex threshold assessment
can be used as a cross-check of auditory function. Evoked
otoacoustic emissions are useful for examining cochlear
(sensory) function. This measure is frequency-specific,
and time- and cost-efficient. Evoked otoacoustic emis-
sions are absent with hearing losses greater than 30 to
40 dB (Prieve, 1992; Robinette, 1992) and the technique
has been used in children with autism (Grewe, Danhauer,
Danhauer, & Thornton, 1994). The frequency-specific
Auditory Brainstem Response (ABR) is the single most
useful electrophysiologic procedure for use in estimat-
ing hearing thresholds and has been demonstrated to be
highly correlated with behavioral hearing thresholds in
children who hear normally and in children who have
sensorineural hearing loss (Stapells et al., 1995).
Audiologic assessment should not be delayed in
the differential diagnosis of autism. It is recommended
that audiologic assessment be completed at centers that
have qualified and experienced professional personnel
(pediatric audiologists) who have current test methods
and technologies readily available. It is recommended
that facilities without these components enter con-
sortial arrangements with centers that are able to pro-
vide this type of comprehensive assessment of children
When hearing loss (conductive or sensorineural) is
detected, the child should be referred to an otolaryngol-
ogist, but concerns raised at the Level 1 screen regard-
ing other developmental indicators ('red flags") for
autism (e.g., lack of social relationships, unusual be-
haviors) must not be ignored. The audiologist, speech-
language pathologist, and medical practitioner's follow-
up of the child should include surveillance for indicators
of autism. When appropriate, in-depth assessment (psy-
chological, sensorimotor) should be recommended in
order to address the potential co-occurrence of autism
and hearing loss.
Transient, fluctuant conductive hearing loss asso-
ciated with otitis media with effusion can co-occur in
children with autism. Audiologic and medical follow-
up for conductive hearing loss associated with recur-
rent otitis media is important in the long-term man-
agement of children with autism.
Children with developmental delays who spend an
extended period in the oral-motor stage of play (where
everything "goes into their mouths") are at increased risk
for lead toxicity especially in certain environments. The
prevalence of pica in this group can result in high rates
of substantial and often recurrent exposure to lead and,
quite possibly, other metals (Shannon & Graef, 1997).
Several studies report the neurobehavioral effects and
behavioral toxicity of lead and its potential clinical rel-
evance in patients with autism. Mean blood lead con-
centration was notably higher in 18 children with autism
than in 16 nonautistic children or in 10 normal siblings;
44% of the autistic and psychotic children had blood lead
levels greater than 2 standard deviations above the mean
for normal controls (Cohen, Johnson, & Caparulo, 1976).
In three of six reported cases of lead poisoning in chil-
dren with autism, developmental deviance seemed to
have been present before the possible impact of lead tox-
icity, while in two, the lead poisoning may have con-
tributed to the onset or acceleration of developmental
symptomatology (Accardo, Whitman, Caul, & Rolfe,
1988). A more recent chart review found that 17 chil-
dren with autism were treated for plumbism over a
6-year period from 1987 to 1992. When compared to a
randomly selected group of 30 children without autism
who were treated during the same interval, the children
with autism were significantly older at diagnosis, had a
longer period of elevated blood lead levels during treat-
ment, and 75% were subsequently reexposed despite
close monitoring, environmental inspection, and either
lead hazard reduction or alternative housing (Shannon &
Graef, 1997). Therefore, all children with delays or who
are at risk for autism should have a periodic lead screen
until the pica disappears (Centers for Disease Control
and Prevention, 1997; Shannon & Graef, 1997).
Screening and Diagnosis of Autistic Spectrum Disorders
Specific Screening for Autism
All professionals involved in early child care (pe-
diatricians, neurologists, psychiatrists, psychologists,
audiologists, language pathologists, occupational thera-
pists, and physical therapists) should be sufficiently
familiar with the signs and symptoms of autism to rec-
ognize possible indicators (social, communicative, and
behavioral) of the need for further diagnostic evaluation.
It is important to be aware that children with autism often
are referred for a variety of concerns, such as language
delays, regulatory behavior problems in infancy, motor
or sensory problems, social and behavioral problems,
emotional disturbance, and learning problems.
There are new screening instruments in the field that
focus on children with autism: the Checklist for Autism
in Toddlers (CHAT; Baron-Cohen, Allen, & Gillberg,
1992; Baron-Cohen et al., 1996), the Pervasive Devel-
opmental Disorders Screening Test (PDDST., Siegel,
1998), and for undiagnosed older verbal children, the
Australian Scale for Asperger's Syndrome (Garnett &
Checklist for Autism in Toddlers (CHAT; Baron-
Cohen et al., 1992; 1996) is designed to screen for
autism at 18 months of age, and is also aimed at the pri-
mary care setting. The first section consists of a series
of nine questions to be asked of the parent, such as
whether the child ever demonstrates any pretend play.
The second section consists of a series of five items to
be observed or administered to the child by the provider
during the visit, such as seeing whether the child looks
where you point (joint attention), has any interest in pre-
tend play, or is able to follow a command. Strengths of
the CHAT include its ease of administration and its
demonstrated specificity to symptoms of autism in
18-month-old infants. From both the initial study of sib-
lings of children with Autistic Disorder and from the
larger epidemiological study involving a population
study of 16,000 18-month-old infants, virtually all the
children failing the five-item criterion on the CHAT ad-
ministered twice (1 month apart) were found to have
Autistic Disorder when diagnosed at 20 and 42 months
(Baron-Cohen et al., 1992, 1996; Charman et al., 1998;
Cox et al., 1999). However, the epidemiological study
has indicated that the CHAT was less sensitive to milder
symptoms of autism, as children later diagnosed with
PDDNOS, Asperger, or atypical autism did not routinely
fail the CHAT at 18 months. As a tool for identifying
18-month-olds at risk of autism from a normal popula-
tion, the CHAT appears to be a useful tool, but not an
entirely sufficient tool, for identifying the majority of
children who will fall within the autistic spectrum.
An unpublished variation on the CHAT is The De-
velopmental Checklist, currently under development,
which expands the CHAT into a 30-item checklist that
a parent alone can fill out in about 10 minutes (Robins,
Fein, Barton, & Liss, 1999).
Pervasive Developmental Disorders Screening
Test-Stage 1 (PDDST; Siegel, 1998) is a clinically de-
rived parent questionnaire, divided into three Stages,
each of which is targeted at a different level of screen-
ing. PDDST-Stage 1 is aimed for use in the primary care
setting, with items aimed incrementally from birth to
36 months of age. Unlike the CHAT, this instrument
rates positive as well as negative symptoms, and in-
cludes a number of questions concerning regression. In
addition to sampling similar areas as other scales, the
PDDST also samples temperament, sensory responses,
motor stereotypies, attention, attachment, and peer in-
terest. Parental report of stereotypic behaviors is prob-
ably more accurate than observation, due to the greater
length of observation and varied environments. The tool
was developed in several steps, beginning with a review
of clinical records of a large number of children with
autism. Test-retest and interrater (between parents) re-
liabilities were then used to identify problematic items.
Follow-up clinical diagnosis at age 5 was used to de-
termine the accuracy of screening. Finally, the instru-
ment was administered to a large number of children
with mixed diagnoses to set cutoff scores and algo-
rithms; this work is ongoing. A significant cutoff of
three affirmative answers in PDDST-Stage 1 has been
established for further diagnostic consideration of an
Autistic Spectrum Disorder. This instrument has not yet
been published but is available (see Appendix).
Australian Scale for Asperger's Syndrome (Garnett
& Attwood, 1998) is a parent or teacher rating scale for
high-functioning older children on the autistic spectrum
who remain undetected at school age. It consists of
24 questions rated with a score from 1 to 6, plus a check-
list of 10 additional yes or no behavioral characteris-
tics. If the answer is yes to the majority of questions in
the scale and most of the ratings are between 2 and 6,
a referral for a diagnostic assessment of autism should
Referral to Early Intervention or Local School
As mandated by Public Law 99-457, and reautho-
rized as Public Law 105-17: Individuals with Disabil-
ities Education Act- IDEA (1997), referral for early in-
tervention must be initiated by the Level 1 professional.
Children less than 36 months of age should be referred
Filipek et al.
to the zero-to-three service system in their community;
children ages 36 months and older should be referred
to the local school district.
Level 2: Diagnosis and Evaluation of Autism
Once a child screens positive, he/she then should be
referred for an appropriate assessment by an experienced
clinician, one with expertise in the diagnosis of devel-
opmental disorders. Although numerous studies show
that autism can be reliably diagnosed in preschool chil-
dren, experienced clinicians are usually necessary for ac-
curate and appropriate diagnosis (Gillberg, 1990; Lord,
Storoschuk, Rutter, & Pickles, 1993; Volkmar et al.,
1994). Many children who screen positive and enter into
more comprehensive assessments may NOT, in the end,
necessarily be considered to have autism but may have
a range of other disorders—any of which may merit in-
tervention in their own right. Accordingly, it is impor-
tant that evaluators have a range of experience in the di-
agnosis and assessment of developmental disabilities. In
some cases children may not come to diagnosis in the
preschool years and it is important that screening en-
compass children in the older school-age group as well.
It is therefore the consensus of this Panel that
Level 2 evaluations should be performed only by pro-
fessionals who have specific expertise in the evalua-
tion and treatment of autism.
At the present time no biological marker or simple
laboratory test or procedure exists for the diagnosis of
autism and related conditions. Clinicians must, accord-
ingly, rely on their clinical judgment, aided by guides to
diagnosis such as DSM-IV and ICD-10, as well as by
the results of various assessment instruments, rating
scales, or checklists. The latter instruments do NOT sub-
stitute for the diagnosis by an experienced clinician.
Interdisciplinary collaboration and consultation are
indicated in the diagnosis and assessment of children with
autism and related difficulties. The needs for service from
the various providers will vary depending on the needs
of the child, family, symptomatic presentation, clinical
context, and so forth (Volkmar, Cook, Pomeroy, Real-
muto, & Tanguay, in press). The efforts may involve nu-
merous specialists, including psychologists, neurologists,
speech pathologists and audiologists, pediatricians, child
psychiatrists, occupational therapists, and physical ther-
apists as well as educators or special educators. When
assessments are interdisciplinary in nature, it is critical
that the service providers coordinate their work to avoid
duplication of effort and maximize efficient use of time.
It also is essential that one provider assume a major role
as the "Coordinator of the Assessment."
Research from many studies suggests that the autis-
tic spectrum disorders are not qualitatively different
from Autistic Disorder, but differ primarily in terms of
severity or the presence of repetitive or sensory behav-
iors. This distinction is often confounded by higher ver-
bal skills in individuals with autistic spectrum disorders
other than Autistic Disorder. It is important to insure
that any individual with an autistic spectrum disorder
receive adequate assessments and appropriate diag-
noses. Factors that are not specific to autism, including
degree of language impairment, mental handicap, and
presence of nonspecific behavior disorders such as over-
activity and aggression, significantly affect outcome and
treatment of individuals with autism. Diagnostic eval-
uations must address these issues and provide contin-
ued monitoring of nonspecific as well as autism-related
impairments across development.
In addition to its important role in diagnosis, a com-
prehensive assessment has an essential role in treatment
planning. Although the focus of this paper is on screen-
ing and diagnosis, the other important functions of as-
sessment and treatment are essential. As a practical mat-
ter, the assessment should be concerned not only with
diagnosis as such but with obtaining information on pat-
terns of strengths and weaknesses important to inter-
vention. Indeed the results of the formal assessments are
often not as important as the less formal, but clinically
informative, observations of the child during the as-
sessment. Parents should be intimately involved in this
process. The assessment should also be careful to note
areas of strength as well as weakness.
Expanded Medical and Neurological Evaluation
Birth, Medical, Developmental, and Family Histories
This evaluation would expand on that already per-
formed at Level 1. Besides delineating social, commu-
nication, and behavior characteristics, the focus should
be on the search for acquired brain injury, comorbid con-
ditions, or other medical or neurologic difficulties com-
mon to autism.
Birth History. An increase of only mild obstetrical
complications was noted in the deliveries of autistic in-
dividuals, which was independent of maternal age or
parity, making a causal relationship unlikely (Bolton
et al., 1997). Specifically, no association was found be-
tween autism and gestational age or occurrence of vagi-
nal bleeding, infection, diabetes, toxemia, maternal age,
or prior abortions (Bolton et al., 1997; Cryan, Byrne,
O'Donovan, & O'Callaghan, 1996; Ghaziuddin, Shakal,
& Tsai, 1995; Piven et al., 1993; Rapin, 1996a). There
Screening and Diagnosis of Autistic Spectrum Disorders
was also no association between autism and birth
weight, induction of labor, breech presentation, forceps
or cesarian delivery, prolonged labor, neonatal depres-
sion, need for intensive care or mechanical ventilation,
neonatal seizures, or prolonged neonatal hospitalization
(Bolton et al., 1997; Fein et al., 1997; Piven et al., 1993;
Rapin, 1996a). Although several prior studies indicated
a possible association between autism and increased ob-
stetrical risk factors, although mild, these have not been
borne out (Bryson, Smith, & Eastwood, 1988b; Deykin
& MacMahon, 1980; Finegan & Quarrington, 1979; Fol-
stein & Rutter, 1977a; Folstein & Rutter, 1977b; Gill-
berg & Gillberg, 1983; Levy, Zoltak, & Saelens, 1988;
Lord, Mulloy, Wendelboe, & Schopler, 1991; Mason-
Brothers et al., 1987, 1990; Nelson, 1991; Tsai, 1987).
Many of these studies did not correct for the strong in-
fluence of maternal parity (e.g., reproductive stoppage
effect), which accounted for the differences in at least
two studies (Lord et al., 1991; Piven et al., 1993).
Medical and Developmental History. Detailed his-
tory should be aimed at determining developmental mile-
stones, developmental regression at any age, identifying
any encephalopathic events, history of attention deficit
disorder, seizure disorder, depression, mania, trouble-
some behaviors such as irritability, self-injury, sleep or
eating disturbances, and pica for possible lead exposure.
Family History. Autism, mental retardation, fragile
X syndrome, and tuberous sclerosis should specifically
be inquired about in nuclear and extended family be-
cause of their implications regarding the need for chro-
mosomal or genetic evaluation. In addition, the presence
of affective disorder and anxiety disorder should be in-
vestigated, as these disorders have been shown to be in-
creased in families of autistic individuals and increase
the burden to the family (Bolton et al., 1994; DeLong,
1994; DeLong & Nohria, 1994; Fombonne, Bolton,
Prior, Jordan, & Rutter, 1997; Piven et al., 1990, 1994).
Autism: Family studies have shown that there is a
50- to 100-fold increase in the rate of autism in first-
degree relatives (Rutter, Bailey, Simonoff, & Pickles,
1997; Simonoff, 1998). Recent family studies have shown
that first-degree relatives of autistic probands have ele-
vated rates of social difficulties, characterized by social
withdrawal or awkwardness, and have a higher incidence
of cognitive and executive function deficits, anxiety, and
affective disorders (Bailey, Palferman, Heavey, & Le
Couteur, 1998b; DeLong, 1994; DeLong &, Nohria,
1994; Hughes, Leboyer, & Bouvard, 1997; Piven et al.,
1990, 1991a, 1994, 1997). Extended relatives in both sim-
plex and multiplex families (i.e., those with more than
one autistic child) had a higher rate of social and com-
munication deficits and stereotyped behaviors than did
relatives of children with Down syndrome (Bolton et al.,
1994; Piven, Palmer, Jacobi, Childress, & Arndt, 1997a).
These impairments were milder but qualitatively very
similar to autism, with relatively normal intellectual func-
tion (IQ). In addition, first-degree relatives demonstrated
higher verbal than nonverbal IQ scores, with significant
discrepancies noted between the scores (Fombonne et al.,
1997). The first twin study of 11 monozygotic (MZ) pairs
reported a concordance rate of over 36% for Infantile
Autism, with no concordance in 10 dizygotic (DZ) twin
pairs (Folstein & Rutter, 1977a, 1977b). However, a total
of 82% of these MZ and 10% of the DZ twin pairs were
concordant for some form of cognitive, social, or lan-
guage deficits. A recent study of 28 MZ twin pairs (in-
cluding the original 11 pairs) showed a concordance rate
of 60% for DSM-IV Autistic Disorder, 71% for the
broader spectrum of PDD or Atypical Autism, and 92%
for an even broader phenotype of social and communi-
cation deficits with stereotyped behaviors that nonetheless
were clearly differentiated from normal (Bailey et al.,
1995; Le Couteur et al., 1996).
Fragile X: Numerous early reports noted a highly
significant association between fragile X (FraX) and
autism, in up to 25% of autistic individuals (Blomquist
et al., 1985; Brown et al., 1986; Gillberg &Wahlstrom,
1985; Wahlstrom, Gillberg, Gustavson, & Holmgren,
1986), although this association was and remains con-
troversial (I. L. Cohen et al., 1991). While other stud-
ies report a much lower incidence of FraX (3-7%) in
patients with autism (Bailey et al., 1993a; Bolton &
Rutter, 1990; Piven, Gayle, Landa, Wzorek, & Folstein,
1991b), another study found no evidence of FraX using
cytogenetic (not DNA analysis) techniques (Hashimoto,
Shimizu, & Kawasaki, 1993). Molecular genetic analy-
ses of a large cohort of autistic individuals found FraX
in only three siblings: one girl with Autistic Disorder,
her brother with Atypical Autism, and a second brother
without autistic features but with a learning disability
(Klauck et al., 1997). Because the presence of FraX
genotype did not correlate with the autism phenotype,
they concluded that the association between autism and
fragile X does not exist. Therefore, although few chil-
dren with autism have fragile X syndrome, children
with fragile X syndrome often have autistic sympto-
matology (Feinstein & Reiss, 1998).
Tuberous Sclerosis Complex: Tuberous sclerosis
complex (TSC) is a neurocutaneous disorder that also af-
fects other organ systems, including the heart and kid-
neys. TSC has been linked to two distinct gene loci:
TSC1 to chromosome 9 (9q34) and TSC2 to chromo-
some 16 (16pl3.3) (OMIM™, 1997). The phenotypes of
TSC1 and TSC2 have been considered identical; how-
Filipek et al.
ever, a recent study noted that mental handicap and spo-
radic rather than familial occurrence may be more fre-
quently associated with the TSC2 genotype (Jones et al.,
1997; OMIM™, 1997), although this finding may also
represent an ascertainment bias. Depigmented macules
(shaped like an ash-leaf (Fitzpatrick, 1991)) are usually
the first visible sign of the disease. They are often visu-
alized only with the use of an ultraviolet light (Wood's
lamp). Facial angiofibroma, formerly called adenoma
sebaceum, and shagreen patches over the lower back are
also characteristic, but often do not appear until late
childhood or early adolescence (Webb, Clarke, Fryer, &
Osborne, 1996). The major intracerebral lesions are the
tubers which consist of histiogenic malformations of both
neuronal and glial elements with giant heterotopic cells.
They are characteristically located in the subependymal
regions and in the cortex, predominantly in the frontal
lobes (Braffman & Naidich, 1994; Harrison & Bolton,
1997; Truhan & Filipek, 1993). TSC has been strongly
associated with autism. Estimates suggest that 17% to
over 60% of mentally retarded individuals with TSC are
also autistic, most commonly co-occurring with epilepsy
(Curatolo et al., 1991; Dykens & Volkmar, 1997; Gill-
berg, Gillberg, & Ahlsen, 1994; Harrison & Bolton,
1997; Hunt & Shepherd, 1993; Riikonen & Simell, 1990;
Smalley, Smith, & Tanguay, 1991; Smalley, Tanguay,
Smith, & Gutierrez, 1992). In contrast, the number of
autistic individuals with TSC has been estimated to be
between 0.4 and 3% in epidemiological studies (Dykens
& Volkmar, 1997; Gillberg et al., 1991; Lotter, 1967;
Olsson, Steffenburg, & Gillberg, 1988; Ritvo et al., 1990;
Smalley et al., 1992). This rate increased to 8 to 14% in
autistic subjects with epilepsy (Gillberg, 1991; Riikonen
& Amnell, 1981). A recent report noted an inverse cor-
relation between IQ and the number of tubers identified
on MRI in a small cohort of individuals with TSC; those
individuals with both TSC and autism not only had the
most tubers, but also had tubers located in the temporal
lobes, a finding not seen in nonautistic subjects with TSC
(Bolton & Griffiths, 1997).
Pertinent Positives on the Physical and Neurological
Examination of persons with autism may require
more time because of the likelihood of poor cooperation
by a patient with impaired communication and behav-
ioral problems. Severe unexplained behavioral changes
may be due to an undiagnosed intercurrent illness (e.g.,
dental abscess, gastric ulcer, or ear infection) or an un-
recognized injury. In some individuals, an adequate med-
ical or dental examination may require sedation.
Head Circumference. The head circumference in
children with autism is larger on average than in typi-
cally developing children (Bailey et al., 1995; Bolton
et al., 1994; Davidovitch, Patterson, & Gartside, 1996;
Lainhart et al., 1997; Woodhouse et al., 1996). The same
has been noted with postmortem brain weights (Bailey
et al., 1993b, 1998a; Bauman, 1992b, 1996; Bauman &
Kemper, 1994, 1997; Courchesne, Muller, & Saitoh,
1999). Only a small proportion of children with autism
have frank macrocephaly with head circumferences
above the 98th percentile, but the distribution of the
measures is clearly shifted upward with the mean in
autism falling at about the 75th percentile (Bailey et. al.,
1995; Bolton et al., 1994; Davidovitch et al., 1996; Fili-
pek et al., 1992b; Lainhart et al., 1997; Rapin, 1996b;
Woodhouse et al., 1996). It also appears that a large head
size may not necessarily be present at birth, but may ap-
pear in early to mid-childhood due to an increased rate
of brain growth (Lainhart et al., 1997; Mason-Brothers
et al., 1987, 1990). The phenomenon of a larger head
size without frank neuropathology in children with
autism is widely acknowledged (Bailey et al., 1995;
Bolton et al., 1994; Davidovitch et al., 1996; Lainhart
et al., 1997; Rapin, 1996b; Woodhouse et al., 1996). Bar-
ring lateralizing signs on the remainder of the examina-
tion, routine neuroimaging for the sole finding of a head
circumference greater than the 98th percentile in an
autistic individual is not warranted (Filipek, 1996, 1999;
Filipek, Kennedy, & Caviness, 1992a; Minshew, 1996b;
Minshew & Dombrowski, 1994).
General Examination. Given the high prevalence
of autism in TSC, an examination using a hand-held ul-
traviolet light (Wood's lamp) should be performed on
every child presenting with possible autism as an ini-
tial screen for tuberous sclerosis (Reich, Lenoir, Malvy,
Perrot, & Sauvage, 1997; Smalley et al., 1992). Also,
unusual or dysmorphic features (of facies, limb, stature,
etc) should be noted, for, if present, they suggest the
need for consultation with a geneticist.
Mental Status Examination. The mental status ex-
amination should include the evaluation of social inter-
actions, play, language, and communicative function.
Social interactions should be queried if observation in
the office proves inconclusive. Probes should be included
for age-appropriate friendships, who initiates contact
with the friends (child or parent), interest in other chil-
dren, and the role within the friendship (e.g., leader of
much younger peers or follower of much older peers with
little or no same-aged peers). Deficient play skills are a
hallmark of autism, independent of IQ (Rapin, 1996b).
An adequate period of observation of the child's use of
age-appropriate miniature toys in the examination room
Screening and Diagnosis of Autistic Spectrum Disorders
is essential to discriminate between simple manipulative
(banging or mouthing) or stereotypic (lining up) use of
toys, and actual functional or symbolic (using one item
to represent another) pretend play (Sigman & Ungerer,
1984; Stone, Lemanek, Fishel, Fernandez, & Altemeier,
1990). For example, classifying or sorting miniature fig-
ures, which may be subtle, is a typical stereotypic be-
havior of higher functioning children with autism which
may be mistaken for appropriate play if only given a
Cranial Nerve Examination. Clinical cranial nerve
abnormalities were only infrequently noted in a large
sample of children with autism (Bauman, 1992a; Rapin,
Motor Examination. Impairments of gross and fine
motor function have been reported in autistic individu-
als, and are more severe in those with lower IQ (Rapin,
1996b). Hypotonia was found in about 25% of 176 chil-
dren with autism and in 33% of 110 nonautistic mentally
retarded children, whereas spasticity was found in less
than 5% of either group (exclusionary criteria for this
sample included the presence of lateralizing gross motor
findings). Limb apraxia was noted in almost 30% of
autistic children with normal IQ, in 75% of retarded
autistic children, and in 56% of the nonautistic retarded
control group. A third significant finding was the pres-
ence of observed motor stereotypies in over 40% of chil-
dren with autism (in contrast to a much higher preva-
lence by parental report), and in over 60% of those with
low IQ, but in only 13% of the nonautistic control group.
Autism Diagnostic Tools
The diagnosis of autism as distinct from other de-
velopmental disabilities requires a comprehensive multi-
disciplinary approach. The evaluation should include
measures of parental report, child observation and in-
teractions, and clinical judgment. Assessments should
include cognitive, adaptive behavior, and diagnostic
Diagnostic Parental Interviews/Questionnaires
The Gilliam Autism Rating Scale (GARS; Gilliam,
1995) is a checklist designed to be used by parents,
teachers, and professionals to help both identify and es-
timate the severity of symptoms of autism in individu-
als age 3 to 22 years. Items are based on DSM-IV (APA,
1994) and are grouped into four subtests (a) stereotyped
behaviors (b) communication, (c) social interaction, and
(d) an optional subtest which describes development in
the first 3 years of life. This tool provides a global rat-
ing of autistic symptomatology.
The Parent Interview for Autism (PIA; Stone &
Hogan, 1993) is a structured interview designed to
gather diagnostically relevant information from parents
of young children suspected of having autism. The PIA
consists of 118 items, organized into 11 dimensions as-
sessing various aspects of social behavior, commu-
nicative functioning, repetitive activities, and sensory
behaviors. Items are phrased as questions about spe-
cific observable behaviors, and ratings of the frequency
of occurrence are obtained. Internal consistency and
test-retest reliability were adequate, and concurrent
validity with the DSM (APA, 1994) and the Childhood
Autism Rating Scale (CARS; Schopler, Reichler, &
Rochen-Renner, 1988) was demonstrated. Significant
group differences between young children with autism
and young children with developmental delays or men-
tal retardation were obtained for the total score as well
as the dimensions of Relating, Imitation, Peer Inter-
actions, Imaginative Play, Language Understanding,
and Nonverbal Communication. The PIA takes about
45 minutes to administer.
The Pervasive Developmental Disorders Screen-
ing Test- Stage 2 (PDDST; Siegel, 1998). The PDDST
is a clinically derived parent questionnaire divided into
three Stages, each of which is targeted at a different
level of screening. Further details on this instrument
were included earlier under Level 1 Screening. PDDST-
Stage 2 was developed for Developmental Disorders
Clinics, and PDDST-Stage 3 for Autism or PDD Clin-
ics. Significant cutoffs have been established for fur-
ther diagnostic consideration of an Autistic Spectrum
Disorder: four affirmative answers in PDDST-Stage 2,
and six affirmative answers in PDDST-Stage 3. This
instrument has not yet been published but is available
The Autism Diagnostic Interview-Revised (ADI-R);
Le Couteur et al., 1989; Lord et al., 1993, 1997; Lord,
Rutter, & Le Couteur, 1994) is a comprehensive struc-
tured parent interview that probes for autistic symp-
toms in the spheres of social relatedness, communica-
tion, and ritualistic or perseverative behaviors. It
permits DSM-IV (APA, 1994) and ICD-10 (WHO,
1992, 1993) diagnoses within the autistic spectrum,
with definitive threshold scores for the diagnosis of
Autistic Disorder. The ADI-R (and ADOS-G) are cur-
rently the "gold standard" diagnostic instruments in all
appropriate autism research protocols. Because admin-
istration of the ADI-R takes approximately 1 hour and
requires specific training and validation procedures,
its utility to primary care or clinical specialty profes-
sionals is probably less than its import in the research
Filipek et al.
Diagnostic Observation Instruments
The Childhood Autism Rating Scale (CARS;
Schopler et al., 1988) is a 15-item structured interview
and observation instrument which is suitable for use with
any child over 24 months of age. Each of the 15 items
uses a 7-point rating scale to indicate the degree to which
the child's behavior deviates from an age-appropriate
norm; in addition, it distinguishes mild-to-moderate from
severe autism. The CARS is widely recognized and used
as a reliable instrument for the diagnosis of autism, and
takes approximately 30 to 45 minutes to administer
(Schopler, Reichler, DeVellis, & Daly, 1980).
The Screening Tool for Autism in Two-Year-Olds
(STAT; Stone, 1998a, 1998b) is a theoretically and em-
pirically derived, interactive measure to be administered
to children ages 24 to 35 months by various early child-
hood professionals. The STAT, still in development, is
designed to differentiate autism from other develop-
mental disorders, thus it is a Level 2 screening instru-
ment. In a 20-minute play interaction involving 12 ac-
tivities, the tool samples three areas: play (both pretend
and reciprocal social play), motor imitation, and non-
verbal communicative development. The tasks used on
the STAT were those that best differentiated between
children with autism and those with other developmen-
tal disorders in studies of matched groups of two-year-
olds on a wide range of measures. There is a manual with
clear instructions for administration and scoring. In a
pilot study involving 40 children, the tool correctly clas-
sified 100% of children with autism (n = 8) and 97% of
children with other developmental delays (n = 32) using
a criterion of failure on two of the three areas. Thus,
demonstrating very strong sensitivity and specificity.
Current work on the tool is focused on the empirical
determination of best cutoffs and algorithm scoring.
The Autism Diagnostic Observation Schedule-
Generic (ADOS-G; DiLavore, Lord, & Rutter, 1995;
Lord, 1998; Lord et al., 1989) is a semi-structured ob-
servational assessment in four modules that includes
investigator-directed activities to evaluate communi-
cation, reciprocal social interaction, play, stereotypic
behavior, restricted interests, and other abnormal be-
haviors, in autistic individuals ranging from nonverbal
preschool children to verbal autistic adults. It takes ap-
proximately 30 to 45 minutes to administer. It also per-
mits DSM-IV (APA, 1994) and ICD-10 (WHO, 1992,
1993) diagnoses within the autistic spectrum, with de-
finitive threshold scores for the diagnosis of Autistic
Disorder. As with the ADI-R, administration of the
ADOS-G requires specific training and validation pro-
cedures. As mentioned earlier, the ADOS-G and ADI-R
are the two "gold standard" diagnostic instruments in
all appropriate autism research protocols. Because ad-
ministration of the ADOS-G takes less time than the
ADI-R, many autism specialty professionals are using
this instrument in their clinical practices; albeit pre-
dominantly abroad where clinical time is not as limited
as with managed care in the US.
Differential Diagnosis of Autistic Spectrum
The differentiation of autism from other develop-
mental disorders is accomplished during Level 2. Using
the data collected from the various evaluations, pro-
fessionals must also determine the possible existence
of comorbid disorders. The differential diagnosis of
autism includes consideration of mental retardation not
associated with autism, specific developmental dis-
orders (e.g., of language), and other psychiatric condi-
tions (Volkmar et al., in press).
Mental retardation or borderline intelligence often
coexists with autism. Individuals with severe and pro-
found mental retardation may exhibit various character-
istics that are often associated with autism, particularly
Specific developmental disorders, particularly de-
velopmental language disorders, may mimic autism and
related conditions. Usually in children with language dis-
orders, the primary deficits are in the area of language
or communication, and social skills are typically well-
Schizophrenia occasionally has its onset in early
childhood. Usually there is a history of previously rel-
atively normal development with the onset of charac-
teristic hallucinations and delusions typical of schizo-
phrenia. However, a lack of typical social development
is often part of the premorbid history.
Selective mutism sometimes is confused with
autism and related conditions. In selective mutism the
child's ability to speak in some situations is preserved,
but the child is mute in other situations. The history
and presentation are quite different from that of autism.
Although it is the case that children with autism are
often mute, their mutism is never "selective" nature.
Stereotyped movement disorder is characterized
by motor mannerisms (stereotypies) and the presence
of mental retardation. A diagnosis of stereotyped move-
ment disorder is not made if the child meets criteria for
one of the pervasive developmental disorders.
Dementia occasionally has its onset in childhood.
In some cases the child will fulfill criteria for childhood
disintegrative disorder, in which case that diagnosis as
Screening and Diagnosis of Autistic Spectrum Disorders
well as the specific medical diagnosis causing the de-
mentia can be made. The typical pattern of dementia of
childhood onset is one of progressive deterioration in
mental and motor functioning.
Obsessive compulsive disorder (OCD) presents in
some children with unusual interests and behaviors.
However, social skills are preserved, as are language
and communication skills. When social skill deficits or
communication deficits are present in OCD, they are
qualitatively different from those found in autism.
Schizoid personality disorder is characterized by
relative isolation, with the ability to relate normally in
some contexts. However, personality disorders are not
diagnosed before the age of 18 years by current DSM-
IV standards (APA, 1994).
Avoidant personality disorder is characterized by
anxiety in dealing with social situations.
Reactive attachment disorder usually presents with
a history of very severe neglect or abuse; the social
deficits of reactive attachment disorder tend to remit dra-
matically in response to a more appropriate environment.
Specific Evaluations to Determine the
Language pathologists are independent health care
providers who have responsibilities at the levels of
screening (Level 1), diagnosis and evaluation (Level 2)
of autism. Evaluation at both levels may be accom-
plished in a single session rather than in discrete seg-
ments. Standardized speech, language, and communi-
cation assessments conducted in formal testing situations
may provide important information about specific pa-
rameters of speech and language functioning. However,
such assessments may provide only limited information
about social-pragmatic abilities (i.e., use of language
and communicative abilities in social contexts), which
are characteristically limited in the autistic spectrum
disorders (Allen, 1989; Allen & Rapin, 1992; Lord &
Paul, 1997; Stone, Ousley, Yoder, Hogan, & Hepburn,
1997; Wetherby, Prizant, & Hutchinson, 1998; Wetherby,
Schuler, & Prizant, 1997; Wetherby, Yonclas, & Bryan,
1989). Therefore, a variety of strategies should be
used, including direct assessment, naturalistic observa-
tion, and interviewing significant others, including par-
ents and educators, who can be invaluable sources of
information (Prizant & Wetherby, 1993; Stone & Caro-
Martinez, 1990). Each of these strategies has the poten-
tial to provide qualitatively different information about
a child's speech, language, and communicative abilities
that may ultimately be integrated to develop a profile
for differential diagnosis and intervention planning. Ob-
servations should include a child's interactions with a
variety of persons including family members and peers,
as well as professionals, because variability in commu-
nicative functioning across persons and settings is to be
expected (Wetherby et al., 1997). Specific domains
should be addressed in a comprehensive assessment for
both preverbal and verbal individuals, taking into ac-
count their age, cognitive level, and socioemotional abil-
ities (Wetherby et al., 1998).
Receptive Language and Communication. Clinical
experience suggests that caregivers or professionals
often assume that a child understands others' commu-
nicative signals and may interpret a lack of response to
gestures or speech as noncompliant or uncooperative
behavior. Children's ability to respond to and use com-
municative gestures and vocalizations should be docu-
mented, with and without the support of situational
cues. True linguistic comprehension is evidenced when
children can comprehend words without situational or
nonverbal cues, especially when words refer to persons,
objects, and events outside of the immediate environ-
ment. At higher levels of ability, assessment should ad-
dress comprehension of different simple and complex
sentence types (e.g., negatives, questions, causal, con-
ditional), of ongoing discourse (e.g., ability to under-
stand a story or sequence of events), and of nonliteral
language (i.e., idioms, sarcasm). Guidelines and pro-
cedures for more in-depth assessment of comprehen-
sion for preverbal and verbal individuals are available
(Lund & Duchan, 1993; Miller & Paul, 1995).
Expressive Language and Communication. The
primary focus in this domain is documentation of
(a) communicative means, the behaviors by which a child
expresses intentions, emotions, and physiological states,
and (b) communicative functions, the purposes for which
a child communicates (Prizant & Wetherby, 1993).
Communicative means in preintentional children
may include a variety of nonverbal and vocal behaviors
such as body posture and movement, facial expression,
directed gaze and gaze aversion, and vocalizations. In
developmentally more advanced children, intentional use
of idiosyncratic (e.g., physically leading others) and con-
ventional (e.g., pointing, nodding, waving) gestures, as
well as vocalizations and emerging word forms should
be documented (Schuler, Prizant, & Wetherby, 1997).
Children with autism have been found to have a limited
repertoire of conventional gestures and vocalizations
(Stone et al., 1997; Wetherby et al., 1998), even when
compared to children with other developmental language
Filipek et al.
Communicative functions expressed preverbally or
verbally may include communicating for relatively
nonsocial purposes to have immediate needs met (e.g.,
requesting objects or actions, protesting), or for more so-
cial purposes such as to bring attention to oneself (e.g.,
requesting social routines, greeting, calling) and com-
municating to bring others' attention to interesting
objects or events (e.g., pointing to or commenting on in-
teresting events). Young children with autism com-
municate primarily for relatively nonsocial purposes
when compared to children with developmental language
disorders (Mundy, Sigman, & Kasari, 1990; Wetherby
et al., 1989, 1998). In addition, the rate of communica-
tive acts and a child's ability to persist in repairing com-
munication breakdowns should also be documented. As-
sessment should also document forms and functions of
unconventional nonverbal (e.g., disruptive behaviors) and
verbal (e.g., immediate and delayed echolalia, persever-
ative speech, incessant questioning) communicative be-
havior (Carr & Durand, 1985; Prizant & Rydell, 1993).
For verbal children able to engage in conversation,
collection and analysis of spontaneous language sam-
ples supplement scores on formal language tests (see
below). It provides information about a child's narra-
tive and conversational discourse, including ability to
initiate, maintain, and terminate conversational inter-
actions following acceptable conventions of discourse,
the ability to maintain topic and follow topics intro-
duced by others, and to take the perspective of others
by providing sufficient, but not excessive, amounts of
background or known information (Prizant, Wetherby,
Schuler, & Rydell, 1997).
Voice and Speech Production. Some young children
with autism may not be able to acquire and use speech
as a primary mode of communication, due to severity of
cognitive impairment, severe to profound hearing loss,
or severe language comprehension disorders. Less fre-
quently, specific neuromotor speech disorders are in-
volved, including developmental verbal dyspraxia, a dys-
function in the ability to plan the coordinated movements
to produce intelligible sequences of speech sounds, or
dysarthria, a weakness or lack of control of the oral mus-
culature. For nonspeaking individuals, or for those with
speech of limited intelligibility, assessment should ad-
dress quality and variety of communicative vocalizations
and oral-motor abilities (e.g., chewing, swallowing).
Other aspects of speech to evaluate in more verbal indi-
viduals include prosody, volume, and fluency of speech
production, especially when disturbance in these para-
meters negatively impact on communicative competence.
It is recommended that tests be used for speech-
language-communication assessments (Crais, 1995;
Wetherby & Prizant, 1992) that (1) focus on functions
of communication; (2) analyze preverbal communica-
tion (gestures, gaze, vocalizations); (3) assess social-
affective signaling; (4) profile social, communicative
and symbolic abilities; (5) directly assess the child,
not only rely on parental report; (6) permit observa-
tion of initiated and spontaneous communication, and
(7) directly involve caregivers during the assessment
(Wetherby & Prizant, 1992). The most widely used
tests for children with language and communication
disorders are listed in Table V, which was adapted
from Wetherby and Prizant (1992) and Crais (1995).
The numbers in Table V referring to the relative
strengths and weaknesses reflect the seven points
Although the Level 1 professional may have
obtained a rough estimate of the child's cognitive sta-
tus (mental age) by using screening tools or problem-
solving milestone charts from preprinted well-child
forms and textbooks, knowing the child's cognitive sta-
tus is important in determining his overall level of func-
tioning. This is, in turn, important when trying to es-
tablish a discrepancy between the child's level of social
function and the overall cognitive and adaptive function,
a key criterion in the diagnosis of autism.
As is true of language pathologists, clinical psy-
chologists and developmental pediatricians are inde-
pendent health care providers who have responsibili-
ties at both levels of screening and diagnosis, which
may or may not be accomplished in a single session
rather than as discrete segments. Additional visits may
be necessary for the child to adapt to change as well as
to the newness of the procedures in order to optimize
the chances that the results accurately represent the
child's abilities. While the diagnosis of autism is based
ultimately on clinical symptoms and early history, the
results of cognitive assessment may assist in differen-
tial diagnosis, as well as provide important information
for planning intervention and evaluating its effects. Re-
search has demonstrated specific profiles on cognitive
batteries, with spared performance on tasks that rely on
rote, mechanical, or perceptual processes, and deficient
performance on tasks requiring higher-order concep-
tual processes, reasoning, interpretation, integration or
abstraction (Minshew & Goldstein, 1998). This pattern
is present across multiple cognitive domains, with dis-
sociations between simple and complex processing
demonstrated in areas of language, memory, executive
function, motor function, reading, mathematics, and
Screening and Diagnosis of Autistic Spectrum Disorders
perspective-taking (Klinger & Dawson, 1995; Min-
shew, Goldstein, Taylor, & Siegel, 1994; Ozonoff,
personal communication; Reed & Peterson, 1990; Rum-
sey & Hamburger, 1988). However, few direct com-
parison studies between autism and other disorders
have been conducted and it is possible that other dis-
orders may share some aspects of this information-
processing profile, which accounts for the differences
in behavioral profile.
In terms of intellectual assessment, the Wechsler
Intelligence Scale for Children/WISC-III (1991), and
the Wechsler Adult Intelligence Scale/WAIS-III (1997)
are the tests of choice for higher functioning and older
individuals with relatively good verbal language. Nu-
merous studies have demonstrated a particular pattern
characteristic of autism: performance IQ (PIQ) higher
than verbal IQ (VIQ) and specific inter-subtest scatter,
with Block Design typically the highest subtest and
Comprehension usually the lowest (see Lincoln, Allen,
& Kilmasian, 1995; cited in Lincoln, Allen, & Kilman,
1995a. However, the PIQ-VIQ split is severity de-
pendent. When Full-scale (FSIQ) and VIQ are both
above 70, 80% of autistic individuals will have no sig-
nificant VIQ-PIQ disparity, and the remainder are
evenly divided between those with PIQ>VIQ and those
with PIQ<VIQ (Siegel, Minshew, & Goldstein, 1996).
Thus, there is substantial variability in the intellectual
profiles of people with autism. However, although these
patterns may be typical, they are by no means univer-
sal and cannot be used for diagnostic or differential
diagnostic purposes. No cognitive pattern confirms or
excludes a diagnosis of autism.
Intellectual testing is essential for educational
planning and, for some children, assists in projecting
the long-term level of disability. It is usually benefi-
cial to conduct these evaluations prior to entry into
kindergarten, and to collaborate with educational pro-
fessionals, including school psychologists, in order to
address issues related to curriculum planning and
school performance issues often addressed by school
psychologists. In autism, however, it should be recog-
nized that the predictive validity of such testing is not
There are particular concerns about the validity of
testing younger, lower functioning, and nonverbal chil-
dren. It is critical that care be taken in choosing which
Table V. Strengths and Weaknesses of Specific Language Instrumenta
Evaluation of only receptive language
Peabody Picture Vocabulary Test-Revised
(PPVT-R; Dunn & Dunn, 1981)
Receptive One-Word Picture Vocabulary Test-Revised
(ROWPVT-R; Gardner, 1990b)
Evaluation of only expressive language
Expressive One- Word Picture Vocabulary Test-Revised
(EOWPVT-R; Gardner, 1990a)
Evaluation of both receptive and expressive language
Birth to Three Developmental Scales
(Bangs & Dodson, 1986)
Clinical Evaluation of Language Fundamentals-3
(CELF-3; Semel, Wiig, & Secord, 1995)
Communication and Symbolic Behavior Scales
(CSBS; Wetherby & Prizant, 1993)
MacArthur Communcative Development
Inventories (MCDI; Fenson et al., 1993)
Preschool Language Scale-3 (PLS; Zimmerman,
Steiner, & Pond, 1992)
Scale-Revised (REEL-R; Bzoch & League, 1991)
Rosetti Infant-Toddler Language Scale (1990)
Sequenced Inventory of Communication
Development (SICD; Hedrick, Prather, & Tobin, 1984)
1, 3, 5 limited
1, 2 limited
1, 2 &6 limited
3, 4, 6, 7
3, 4, 7
a The numbers referring to the strengths and weaknesses are based on the seven points outlined in the text.
This table was adapted from Wetherby and Prizant (1992) and Crais (1995).
Filipek et al.
intellectual test to administer to lower functioning or
nonverbal individual with autism (Groden & Mann,
1988; Johnson-Martin, 1988; Klin et al., 1997; Watson
& Marcus, 1988). It is recommended that tests be used
which (1) are appropriate for both mental age and
chronological age; (2) provide a full range (in the lower
direction) of standard scores; (3) sample both verbal
and nonverbal intellectual skills; (4) measure and score
separately verbal and nonverbal skills; (5) provide an
overall index of ability; and (6) have norms which are
current and relatively independent of social function.
With these principles in mind, the most appropriate and
widely used intellectual tests for younger, low- or non-
verbal individuals with autism are listed in Table VI.
Clinical judgment is required to properly interpret
the findings of these measures for the purpose of dif-
ferential diagnosis. Additional information regarding
assessment and interpretation of psychological meas-
ures is provided in other resources (Jacobson & Mulick,
1996; Marcus, Lansing, & Schopler, 1993; Marcus &
Adaptive Behavior Evaluation
It is essential that a measure of adaptive function
(the capability for self-sufficiency in acticities of daily
living) be collected by the psychologist for any child
evaluated for an associated mental handicap. Diagno-
sis of mental retardation relies upon both subaverage
intellectual functioning (IQ < 70) and concurrent
deficits in adaptive functioning (APA, 1994).
The Vineland Adaptive Behavior Scales (VABS;
Sparrow, Balla, & Cicchetti, 1984b) are considered to
be the most widely used instrument to assess adaptive
behavior (Klin et al., 1997). The scales offer an estimate
of adaptive development in the domains of Socialization
(interpersonal relationships, play and leisure time, and
coping skills); Daily Living Skills (personal, domestic,
and community skills); Motor Skills (gross and fine
motor); and Communication (receptive, expressive, and
written communication), with developmentally ordered
skills for each area. There are three available versions
of the Vineland: (a) a survey form used as a diagnostic
and classification tool for children and adults (Sparrow
et al., 1984b); (b) an expanded form for use in develop-
ing educational or rehabilitation plans (Sparrow, Balla,
& Cicchetti, 1984a); and (c) a classroom edition to be
used by teachers (Sparrow, Balla, & Cicchetti, 1985).
Standard scores, percentile ranks, adaptive levels, and
age equivalents are available. The expanded edition is
the most useful for autistic children, whose adaptive
function is usually lower than their cognitive level (Volk-
mar, Carter, Sparrow, & Cicchetti, 1993a). Recent sup-
plementary norms have been published for individuals
with autism (Carter et al., 1998).
The Scales of Independent Behavior-Revised (SIB-
R; Bruininks, Woodcock, Weatherman, & Hill, 1996) is
a comprehensive norm-referenced assessment of adap-
Table VI. Strengths and Weaknesses of Specific Cognitive Instrumentsa
Bayley Scales of Infant
Development II (1993)
Mullen Scales of Early
Leiter-Revised (Roid &
& Sattler, 1986)
1 : <42 months
1 : <60 months
highlights visual strengths
of autistic individuals
3: verbal section is limited
1 : extends from preschool
1: not normed for >42 months
2: standard score (SS) > 50
4: also mixes in social cannot
always establish basal score
1: basal score = 24 months
3: nonverbal only
1: basal score = 18 months
2: SS to 45 only
1: basal score = 24 months
2: SS to 70 only— highly
verbal, long administration
a The numbers referring to the strengths and weaknesses are based on the six points outlined in the
Screening and Diagnosis of Autistic Spectrum Disorders
live and maladaptive behavior, for ages ranging from
infancy through elderly adulthood. Fourteen Adaptive
Behavior Clusters are offered in three forms: Early
Development Form (15-20 minutes), Short Form (15-
20 minutes), Full-scale Form (45-60 minutes). These
cover motor skills, social interaction and communication
skills, personal living, self-care, and community living
skills. Age-equivalent scoring tables are included in the
response booklets for each subscale, allowing examiners
to get immediate developmental information.
Sensorimotor Assessment and Occupational Therapy
Sensorimotor Assessment: Diagnostic practice has
conventionally placed little emphasis on the assessment
of Sensorimotor behaviors in autism, with the excep-
tion that stereotypies are part of a "restricted behav-
ioral repertoire" (APA, 1994; Lord, 1995). The reasons
for this include the facts that there is a dearth of sys-
tematic empirical research in this domain and that the
existing literature is controversial with respect to the
usefulness of these variables for the differential diag-
nosis of autism. Thus, it seems particularly important
to document qualitative dimensions of early sensory
processing and motor behaviors (through both obser-
vation and parent report) rather than simply assess
motor milestones during infant screenings.
Evaluation of Sensorimotor functions should focus
on the detection and localization of underlying neuro-
logic deficits, whereas occupational therapists have spe-
cific expertise in the evaluation of their impact on the
individual's functional skills or daily activities. Evalua-
tion of motor skills is particularly important in situations
where there is a question of delay, dysfunction, or re-
gression in such skills, to document areas of strength as
well as weakness for prognostic and intervention plan-
ning. Assessment of gross and fine motor skills may be
completed by qualified professionals (e.g., occupational
therapists or physical therapists) with a variety of stan-
dardized tools appropriate to the developmental level of
the individual with autism; however, adaptations may be
needed if the person with autism has difficulty under-
standing the tasks or is uncooperative. More important,
qualitative observations of praxis (e.g., planning or se-
quencing of novel complex movement patterns; imita-
tion of movements or pantomime; organization of goal-
directed actions with materials in the environment) are
a critical part of the sensorimotor evaluation for
individuals with autism because these abilities are often
deficient (Rogers, Bennetto, McEvoy, & Pennington,
1996; Stone & Lemanek, 1990), and require specific
interventions. Repetitive motor stereotypies, unusual pos-
turing, object stereotypies, and self-injurious behaviors
(SIBs) should be routinely documented through parental
report or observation. Hand or finger mannerisms, body
rocking, and other motor disturbances such as unusual
posturing, are commonly reported in 37-95% of subjects
studied (Adrien, Ornitz, Barthelemy, Sauvage, & Lelord,
1987; Elliott, 1990; Le Couteur et al., 1989; Ornitz,
Guthrie, & Farley, 1977), and often manifest during the
preschool years (Lord, 1995). The development of stereo-
typies, particularly in severe forms (e.g., SIB), may pro-
foundly influence individual outcomes and prognosis for
treatment in children with autism.
Sensory processing abilities are also prominently
aberrant in autism. Preoccupations with sensory features
of objects, sensory modulation difficulties reflected in
over- and underresponsiveness to environmental stimuli,
and paradoxical responses to sensory stimuli, among oth-
ers, have been reported in 42-88% of persons with autism
studied (Elliott, 1990; Kientz & Dunn, 1997; Le Couteur
et al., 1989). Sensory processing requires assessment by
expert clinical observations in tandem with parent reports
or questionnaires because these disruptions may impact
strongly on performance in daily activities.
The Sensory Integration and Praxis Tests (Ayres,
1989) are not routinely warranted as part of diagnostic
evaluations of children with autism. However, this bat-
tery of tests may be prescribed on an individual basis
to detect specific patterns of sensory integrative dys-
function in children between the ages of 4 and 9 years
with average cognitive functioning.
Occupational Therapy Evaluation. The occupa-
tional therapist, as part of the evaluation team, should
make a determination about the necessity to screen and
fully evaluate an individual with autism about whom
there are concerns regarding functional skills or occu-
pational performance (i.e., goal-directed everyday rou-
tines). It is important that the occupational therapist have
a comprehensive understanding of autism and be expe-
rienced in assessing persons in the age range of the clients
being seen (e.g., child vs. adult). The occupational ther-
apist first and foremost evaluates performance specifi-
cally in the areas of play or leisure, self-maintenance
through activities of daily living, and productive school
or work activities. Play is often disrupted in young chil-
dren with autism (Restall & Magill-Evans, 1994; Stone
& Lemanek, 1990) and particularly warrants assessment
in a naturalistic context. Second, the occupational ther-
apist should consider any specific performance compo-
nents or contexts that may be impacting on the individ-
ual's daily functioning because this information is critical
to the team diagnostic process as well as to an appropri-
Filipek et al.
ate individualized intervention plan. Among specific
components noted to be problematic, but not necessarily
specific, to persons with autism, are complex motor
planning abilities (Mailloux, Parham, & Roley, 1998;
Minshew et al., 1997), sensory processing abilities
(Adrien et al., 1993; Baranek, 1999; Dahlgren & Gill-
berg, 1989; Kientz & Dunn, 1997; Ornitz et al., 1977),
imitation skills (Rogers et al., 1996; Stone & Lemanek,
1990), social and interpersonal skills (Gillberg et al.,
1990; Stone & Hogan, 1993; Volkmar et al., 1993a), and
coping with behavioral rigidities or restricted interests
(Baranek, Foster, & Berkson, 1997). Supplemental in-
terviews and parental reports should be used to corrob-
orate observational findings or standardized assessments,
particularly if those assessments were performed outside
of the individual's typical routines and environments.
Neuropsychological, Behavioral, and Academic
Psychologists trained in evaluating autistic individ-
uals can play a critical role in intervention planning, out-
come assessment, and the diagnosis and treatment of co-
morbid psychological conditions. Standardized measures
are used to establish baseline function in many domains
of learning, performance, and socialization. Behavioral
assessment by direct observation is used to address spe-
cific learning and behavior problems, to establish the
functional or controlling relations of inappropriate be-
havior, to track behavioral progress, and to document the
effectiveness of intervention. These are specialized psy-
chological services, requiring appropriate training and
experience. Specific assessments may address a child's
psychological profile, motivation or reinforcement pref-
erences, learning style, sensory and motor characteristics
(and associated abnormalities), specific social skills
deficits, academic skills, ritualistic or stereotyped pat-
terns of behavior, and life-style and family relationships.
Recent research suggests that specific neuropsy-
chological impairments can be identified in children in
early childhood and that such impairments are correlated
with the severity of autistic symptoms (Dawson, 1996;
Dawson, Meltzoff, Osterling, & Rinaldi, 1998). Among
the diverse types of neuropsychological impairments that
may be exhibited by children with autism are deficits in
explicit memory, in establishing rules governing reward
contingencies, and in working memory, planning, and
response inhibition (Dawson, 1996). Thus, it can be use-
ful to assess a range of neuropsychological functions, in-
cluding attention, memory, praxis, language and visual-
spatial processing, so that educational strategies can
address each child's specific strengths and weaknesses.
Assessment of Family Functioning and Resources
The family is a child's best resource. Parental in-
tervention and behavior management strategies provided
by a psychologist have a strong impact on the child's de-
velopmental status and autistic symptoms. Parental stress
and exhaustion can adversely affect the child's well-
being. Thus evaluation of the child must take place
within the context of his or her family. One must deter-
mine the parents' level of understanding of their child's
condition and offer appropriate counseling and educa-
tion. One must determine if the family has informal sup-
ports, such as extended family, neighbors, or friends to
assist them in their child-rearing responsibilities. The
family's readiness to meet other families of children with
similar conditions must also be assessed. Often families
learn more and communicate more with other families
than they do with professionals. Finally, based on the
family's socioeconomic status and the status of the child,
one must evaluate the need for and availability of vari-
ous social services to provide respite and other supports.
Social workers, psychologists, or other profession-
als who specialize in families of autistic individuals may
be best able to assess the family dynamics in relation to
parenting and behavior management strategies as they
specifically relate to the autistic child. These profes-
sionals may also know additional resources specifically
tailored to families of autistic individuals. Finally, they
themselves may facilitate parent support groups and
plan parent seminars. This assessment will focus on the
specific issues relating to the type of developmental pro-
file identified during the Level 2 evaluation. It cannot be
overemphasized that the family is the child's best re-
source. Although there may be several confounding vari-
ables affecting a child's overall adult outcome, most
autism specialists would agree that the family does play
a very important role. This expanded assessment can also
help determine the quality and quantity of community
resources, educational programs and networking that a
particular family needs. Each family is unique in its
search for support and knowledge.
Level 2 Laboratory Investigation
A wide range of biochemical determinations have
been performed in urine, blood, and cerebrospinal fluid
in an attempt to identify a specific metabolic abnormal-
ity in individuals with autism. Included are studies of in-
born errors in amino acid, carbohydrate, purine, peptide,
and mitochondrial metabolism, as well as toxicological
Screening and Diagnosis of Autistic Spectrum Disorders
studies. The reported co-occurrence of autistic-like
symptoms in individuals with inborn errors of metab-
olism has led to consideration of screening tests as part
of the routine assessment of patients with severe de-
velopmental impairment (Steffenburg, 1991). However,
the percentage of children with autism who prove to
have an identifiable metabolic disorder is probably less
than 5% (Dykens & Volkmar, 1997; Rutter, Bailey,
Bolton, & Le Couteur, 1994; Rutter et al., 1997). Most
of the biochemical analyses are useful at present only
as research tools in the ongoing effort to understand
the biology of autism.
Metabolic testing or consultation is indicated by a
history of lethargy, cyclic vomiting, early seizures, dys-
morphic or coarse features, mental retardation or if men-
tal retardation cannot be excluded, questionable new-
born screening, or birth out of the US because of the
potential absence of newborn screening and maternal
public health measures. As recommended by the Amer-
ican College of Medical Genetics, selective metabolic
testing should be initiated only in the presence of sug-
gestive clinical and physical findings (Curry et al., 1997).
Of the chromosomal disorders found in associa-
tion with autism, the most common abnormality de-
scribed in recent studies is that involving the proximal
long arm of chromosome 15 (15ql l-q13), occurring in
1 to 4% of consecutive cases meeting criteria for Autis-
tic Disorder (Cook et al., 1998; Gillberg, 1998). These
are usually maternally inherited duplications, either
pseudodicentric 15 (inverted duplication 15) or other
atypical marker chromosomes, with one or two extra
copies of the area roughly corresponding to the typical
Angelman syndrome (AS)/Prader Willi syndrome
(PWS) deletion region of approximately 4 million base
pairs. The 15q patients typically have moderate to pro-
found mental retardation. In samples of patients with
autistic disorder whose IQ was greater than 35, inter-
stitial duplications of 15q11-13 have been found in
more than 1% of patients and at a greater frequency
than fragile X or other currently identifiable chromo-
somal disorders (Cook et al., 1998; Gillberg, 1998; Per-
icak-Vance et al., 1997; Schroer et al., 1998; Weidmer-
Mikhail, Sheldon, & Ghaziuddin, 1998).
Angelman syndrome, usually due to an absence
(deletion) of maternally inherited 15q11-q13 material,
has been found in patients with autism and profound men-
tal retardation (Gillberg, 1998; Schroer et al., 1998; Stef-
fenburg, Gillberg, Steffenburg, & Kyllerman, 1996).
Autism has also been found in patients with PWS (Demb
& Papola, 1995), although at a decreased rate relative to
the frequency of autism in Angelman syndrome or du-
plications of 15ql 1-13. Confirmation by FISH probes for
the PWS/AS region is necessary to confirm cytogenetic
evidence of 15q11-13 abnormalities.
DNA analysis for fragile X and high resolution chro-
mosome studies (karyotype) are indicated for a diagno-
sis of autism, mental retardation (or if mental retardation
cannot be ruled out), if there is a family history of frag-
ile X or undiagnosed mental retardation, or if dysmor-
phic features are present (American College of Medical
Genetics: Policy Statement, 1994). It should be under-
stood, however, that there is little likelihood of positive
karyotype or fragile X testing in the presence of high-
functioning autism. The absence of a positive genetic test
does not exclude a genetic basis for autism. If the indi-
cations for DNA analysis for fragile X and high resolu-
tion chromosome studies are present but the family de-
clines genetic testing, the family should be counseled to
inform extended family members of the potential gene-
tic risks of this disorder so they may seek appropriate
In addition, the recurrence risk of autism is esti-
mated to be between 3 and 7% across several studies
(Bolton et al., 1994; Jorde et al., 1990; Piven et al., 1990;
Szatmari et al., 1993).Therefore, although there is no
current method to detect autism prenatally, parents
should be counseled about the almost 50-fold increased
risk of having a second child on the autistic spectrum
(1 in 20 to 1 in 10, as compared with 1 in 1,000 to 1 in
500 for the general population).
The prevalence of epilepsy in a large cohort of pre-
school children with autism has been estimated as 7%
(Rapin, 1996a), in another cohort, 14% (Tuchman et al.,
1991b), and the cumulative prevalence by adulthood is
estimated at 20 to 35% (Minshew et al., 1997). The peaks
of seizure onset occurred in early childhood and again in
adolescence (Gillberg & Steffenburg, 1987; Lockyer &
Rutter, 1970; Minshew et al., 1997; Rossi, Parmeggiani,
Bach, Santucci, & Visconti, 1995; Volkmar & Nelson,
1990; Wong, 1993). Mental retardation, with or without
motor abnormalities and family history of epilepsy, was
a significant risk factor for the development of seizures
in autistic individuals. The relationship between autism
with an early regressive course (before 36 months), CDD
(after 36 months), Landau-Kleffner syndrome (Landau
& Kleffner, 1957, 1998), and electrical status epilepti-
cus during slow wave sleep (ESES) is currently poorly
understood, as are their underlying etiologies and patho-
Filipek et al.
physiologies (Bristol et al., 1996; Tuchman & Rapin,
1997). Regression in adolescence associated with seizure
onset has also been reported, with further loss of lan-
guage and cognitive skills (Lockyer & Rutter, 1970), but
little is known about its cause or prevalence (Minshew
et al., 1997).
Seizures may be of all types, but partial complex
seizures seem to be more prevalent, with EEG abnor-
malities occurring most often over the temporal lobes
(Olsson et al., 1988). The recognition of complex par-
tial seizures in autistic individuals is complicated by
the tendency to blame unusual behaviors on autism, and
by the lack of direct correlation between clinical
seizures and EEG paroxysmal activity (Minshew et al.,
1997). In addition, a recent study suggests that there
may be a casual relationship between a subgroup of
children with autistic regression and EEG-defined "be-
nign focal epilepsies" (Nass, Gross, & Devinsky, 1998).
Any behaviors such as staring, cessation of activity, or
aggressive escalations associated with confusion should
trigger a high index of suspicion of complex partial
seizures in autistic individuals.
Indications for a prolonged sleep-deprived EEG
with adequate sampling of slow wave sleep include
evidence of clinical seizures, history of regression (clin-
ically significant loss of social and communicative func-
tion) at any age but especially in toddlers and pre-
schoolers, and in situations where there is a high index
of clinical suspicion that epilepsy, clinical or subclini-
cal, may be present. There is inadequate evidence at the
present time to recommend EEG studies in all individ-
uals with autism (Rapin, 1995, 1997; Rossi et al., 1995;
Tuchman, Jayakar, Yaylali, & Villalobos, 1997; Tuch-
man, 1994, 1995; Tuchman & Rapin, 1997; Tuchman
et al., 1991b.)
Except for the specific tests noted earlier, event-
related potentials (Ciesielski, Knight, Prince, Harris, &
Handmaker, 1995; Kemner, Verbaten, Cuperus, Cam-
fferman, & Van Engeland, 1994; Kemner, Verbaten, Cu-
perus, Camfferman, & van Engeland, 1995; Lincoln,
Courchesne, Harms, & Allen, 1995b; Rapin & Dunn,
1997; Verbaten, Roelofs, van Engeland, Kenemans, &
Slangen, 1991) and magnetoencephalography (Chuang,
Otsubo, Hwang, Orrison, & Lewine, 1995; Morrell et al.,
1995; Salmelin, Service, Kiesila, Uutela, & Salonen,
1996) are considered to be research tools in the evaluation
of autism, without evidence of routine clinical utility at
Computed tomographic (CT) studies during the
1970s and 1980s reported a wide range of brain imaging
abnormalities, which contributed to the then prevalent
view that most cases of autism would ultimately be
found to be attributable to an underlying structural dis-
order. This perspective of autism, together with the gen-
eral clinical practice in child neurology of including CT
scanning in the search for etiologies of unexplained de-
velopmental delay in young children, led to the stan-
dardization of CT as part of the assessment of children
diagnosed with autism during the 1970s and 1980s. This
perspective changed substantially as a result of the
landmark study of Damasio et al. (1980) demonstrating
that CT abnormalities of the brain in autistic individu-
als were associated only with the presence of coexist-
ing disorders rather than with autism itself. In a review
of over 400 imaging studies in autistic subjects, a very
low prevalence of focal lesions or other abnormalities
was reported, and their inconsistent localization marked
them as coincidental (Filipek et al., 1992a). In a subse-
quent study, the prevalence of lesions on MRI in the
children with autism was equal to that in the normal
control volunteers (Filipek et al., 1992b). A series of
CT and magnetic resonance imaging (MRI) studies of
autistic subjects screened to exclude those with identi-
fiable disorders other than autism (see reviews by Min-
shew et al., 1994, 1996b, Filipek et al., 1992a, 1996,
1999) have confirmed the absence of significant de-
tectable brain abnormalities characteristic of autism.
The clinical perception that structural brain imaging
should be routinely included in the assessment to iden-
tify gross brain abnormalities causing autism is, there-
fore, no longer viewed as valid (Filipek, 1999).
Functional imaging studies are a research endeavor
in autism and do not have a role in clinical diagnosis at
the present time. With the advent of functional imaging
methods, such as functional MRI (fMRI), single photon
emission tomography (SPECT), and positron emission
tomography (PET), such studies are expected to play a
major role in defining the brain basis for the behavioral
impairments in autism, but as research tools only. The
value of such studies will depend heavily on the design
of activation paradigms, the documentation of the task
demands of the paradigms for the individual, and the in-
terpretation of the findings within the broader context of
what is known about neurobehavioral function in autism.
One construct of growing value in this regard is the cog-
nitive model of autism as a selective disorder of complex
information-processing abilities and as a disorder of mul-
tiple primary deficits (Minshew & Goldstein, 1998).
The presence of neurologic features not explained
simply by the diagnosis of autism (e.g., asymmetric
motor examination, cranial nerve dysfunction, severe
headache) may be an indication for imaging, in which
case the usual standards of practice apply (Filipek, 1999).
Screening and Diagnosis of Autistic Spectrum Disorders
Autism per se is not considered an indication for neuro-
imaging, even in the presence of megalencephaly.
Tests of Unproven Value
There is inadequate evidence to support routine
clinical testing of individuals with autism for hair analy-
sis for trace elements (Gentile, Trentalange, Zamichek,
& Coleman, 1983; Shearer, Larson, Neuschwander, &
Gedney, 1982; Wecker, Miller, Cochran, Dugger, &
Johnson, 1985), celiac antibodies (Pavone, Fiumara, Bot-
taro, Mazzone, & Coleman, 1997), allergy testing (in
particular food allergies for gluten, casein, Candida and
other molds) (Lucarelli et al., 1995), immunological or
neurochemical abnormalities (Cook, Perry, Dawson,
Wainwright, & Leventhal, 1993; Singh, Warren, Averett,
& Ghaziuddin, 1997; Yuwiler et al., 1992), micronutri-
ents such as vitamin levels (Findling et al., 1997; LaPer-
chia, 1987; Tolbert, Haigler, Waits, & Dennis, 1993),
intestinal permeability studies (D'Eufemia et al., 1996),
stool analysis, urinary peptides (Le Couteur, Trygstad,
Evered, Gillberg, & Rutter, 1998), mitochondrial dis-
orders (including lactate and pyruvate) (Lombard, 1998),
thyroid function tests (D. J. Cohen, Young, Lowe, &
Harcherik, 1980; Hashimoto et al., 1991), or erythrocyte
glutathione peroxidase studies (Michelson, 1998).
Referral to Early Intervention
Again, the Level 2 clinicians should refer to an ap-
propriate early intervention or school team if the Level
1 clinicians did not do so. If the child is, indeed, en-
rolled in a program, the results of Level 2 evaluations
by the psychologist, speech and occupational therapists
should be communicated to the staff in an effort to bet-
ter tailor their intervention strategies to the particular
needs of the child.
Level 1: Routine Developmental Screening
1. All professionals involved in early child care
(pediatricians, neurologists, psychiatrists, psycholo-
gists, audiologists, language pathologists, physical ther-
apists, and occupational therapists) should be suffi-
ciently familiar with the signs and symptoms of autism
to recognize possible social, communicative, and be-
havioral indicators of the need for further diagnostic
2. Developmental screening should be performed
at each and every well-child visit throughout infancy,
toddlerhood, the preschool years, and at any age there-
after if concerns are raised about social acceptance, learn-
ing and behavior. Recommended screening tools include
The Ages and Stages Questionnaire (ASQ), The BRIG-
ANCE® Screens, The Child Development Inventories
(CDIs), and the Parents' Evaluation of Developmental
Status (PEDS). Also recommended is the use of Specific
Developmental Probes, as outlined in the text, to specif-
ically identify any parental concerns about development.
The Denver-H (formerly the Denver Developmental
Screening Test-Revised) is not recommended as an ap-
propriate developmental screen in this capacity.
3. The following developmental milestones are
nearly universally present by the age indicated. Failure
to meet any of these milestones is an absolute indication
to proceed with further evaluations. Delay in referral for
such testing may delay early diagnosis and treatment and
affect the long-term outcome.
No babbling by 12 months.
No gesturing (pointing, waving bye-bye, etc) by
No single words by 16 months.
No 2-word spontaneous (not just echolalic)
phrases by 24 months.
Any loss of any language or social skills at any
4. Level 1 Laboratory Investigations. Concern re-
garding a speech, language, or hearing problem by par-
ent or practitioner should prompt an immediate referral
for a formal audiologic assessment, regardless of whether
the child "passed" a neonatal hearing screen.
Audiological assessment should be performed at
centers with qualified and experienced pediatric audi-
ologists, with current audiological testing methods and
technologies. Facilities without these qualifications
should enter consortial arrangements with centers that
are able to provide this type of comprehensive assess-
ment of children with autism.
Periodic lead screens should be performed in any
autistic child with pica.
5. Professionals involved in early child care should
also become familiar with and use one of the screening
instruments for children with autism (e.g., the Checklist
for Autism in Toddlers (CHAT), the Pervasive Devel-
opmental Disorders Screening Test (PDDST), or, for
older verbal children, the Australian Scale for Asperger's
6. The social, communication and play develop-
ment and behavior of siblings of children with autism
needs to be monitored very carefully not only for autism-
related symptoms but also for language delays, learning
difficulties, and anxiety or depressive symptoms.
7. As mandated by Public Law 99-457, and re-
authorized as Public Law 105-17: Individuals with Dis-
abilities Education Act- IDEA (1997), a referral for
Filipek et al.
early intervention should be initiated by the primary care
practitioner. Children less than 36 months of age should
be referred to the zero-to-three service system in their
community; children ages 36 months and older should
be referred to the local school district.
8. Health care providers and others need to increase
their comfort level in talking with families about autism,
which is a treatable disorder with a wide range of out-
comes. Thus, information about the benefits of early in-
tervention for children with autism needs to be widely
disseminated to health care professionals and others
working with young children and families.
9. Screening tools for older children with milder
symptoms of autism need to be made widely available
in educational and recreational settings, where these
children's difficulties are often most visible, as well as
in health and allied health settings. Pediatricians can
and should play an important role in raising a suspi-
cion of autism, paving the way to appropriate referral
to professionals knowledgeable about autism in verbal
Level 2: Diagnosis and Evaluation of Autism
1. It is the consensus of this Panel that Level 2
Diagnosis and Evaluation should be performed by pro-
fessionals who specialize in the treatment of children
2. The diagnosis of autism should be accurately
made based on clinical and DSM-IV criteria, and should
include the use of a diagnostic instrument with at least
moderate sensitivity and good specificity for autism.
Sufficient time must be planned for both a stan-
dardized parent interview regarding current concerns
and behavioral history related to autism, and direct,
structured observation of social and communicative be-
havior and play.
Such interview instruments include the Gilliam
Autism Rating Scale (GARS), The Parent Interview for
Autism (PIA), The Pervasive Developmental Disorders
Screening Test- Stage 2 (PDDST), or the Autism Diag-
nostic Interview-Revised (ADI-R).
Direct, structured observation instruments include
the Screening Tool for Autism in Two-Year-Olds (STAT),
the Childhood Autism Rating Scale (CARS), and the
Autism Diagnostic Observation Schedule-Generic
3. Individuals with even mild autism must also re-
ceive adequate assessments and appropriate diagnoses,
using practice standards similar to those outlined above.
4. Diagnostic evaluations must also address those
factors that are not specific to autism, including degree
of language impairment, mental handicap, and presence
of nonspecific behavioral disorders such as overactivity,
aggression, anxiety, depression, or specific learning dis-
abilities, which can significantly affect outcome and
treatment of autistic individuals.
5. An expanded medical and neurological evalua-
tion whose focus is on the search for acquired brain in-
jury, comorbid condition, or difficulties common in
autism: pregnancy, delivery, perinatal history, develop-
mental history including milestones, regression in early
childhood or later in life, encephalopathic events, atten-
tion deficit disorder, seizure disorder (absence or gen-
eralized), depression or mania, troublesome behaviors
such as irritability, self-injury, sleep and eating distur-
bances, and pica for possible lead exposure.
Family History should specifically probe in nuclear
and extended family for autism, mental retardation, frag-
ile X syndrome, and tuberous sclerosis complex, because
of their implications regarding the need for chromoso-
mal or genetic evaluation. In addition, family members
with affective or anxiety disorder should be identified,
as these impact on the care of the child and family bur-
den. The focus of the physical and neurological exami-
nation should include: longitudinal measurements of
head circumference, unusual features (facial, limb,
stature, etc.) suggesting the need for genetic evaluation,
neurocutaneous abnormalities (requiring an ultraviolet
Wood's-lamp examination), gait, tone, reflexes, cranial
nerves, and mental status including verbal and nonverbal
language and play.
6. A speech-language-communication evaluation
should be performed on all children who fail language
developmental screening procedures, by a language
pathologist with training and expertise in evaluating chil-
dren with autism.
A variety of strategies should be used in this as-
sessment, including but not limited to direct standard-
ized instruments, naturalistic observation, parental in-
terviews, and procedures focusing on social-pragmatic
Results of a speech-language-communication
assessment should always be interpreted relative to a
child's cognitive, motor and socioemotional abilities.
7. A cognitive evaluation should be performed in
all children with autism by a psychologist or develop-
mental pediatrician experienced in autism testing, and
should include assessment of family (parent and sib-
ling) strengths, talents, stressors, and adaptation, as
well as resources and supports. Psychologists working
with children with autism should be familiar with a
range of theories and approaches specific to this pop-
Screening and Diagnosis of Autistic Spectrum Disorders
Psychological instruments should be appropriate for
the mental and chronological age, should provide a full
range (in the lower direction) of standard scores, in-
cluding independently scored measures of verbal and
nonverbal abilities, should provide an overall index of
ability, and should have current norms which are inde-
pendent of social ability.
8. A measure of adaptive functioning should be col-
lected by the psychologist for any child evaluated for an
associated mental handicap. Recommended instruments
include the Vineland Adaptive Behavior Scales and the
Scales of Independent Behavior-Revised (SIB-R).
9. Screening and full evaluation for sensorimotor
skills by qualified professionals (occupational thera-
pists or physical therapists) with expertise in testing
persons with autism should be considered, including an
assessment of gross and fine motor skills, praxis, sen-
sory processing abilities, unusual or stereotyped man-
nerisms, and the impact of these components on the
autistic person's life.
10. An occupational therapy evaluation is indicated
when an autistic individual is experiencing disruptions
in functional skills or occupational performance in the
areas of play or leisure, self-maintenance through activ-
ities of daily living, or productive school and work tasks.
The occupational therapist may evaluate these per-
formance areas in the context of different environments,
and through activity analysis, the contributions of per-
formance component abilities (e.g., sensory processing,
fine motor skills, social skills) in goal-directed everyday
11. A neuropsychological, behavioral, and aca-
demic assessment should be performed, in addition to
the cognitive assessment, to include communication
skills, social skills and relationships, educational func-
tioning, problematic behaviors, learning style, moti-
vation and reinforcement, sensory functioning, and
12. Assessment of family functioning should be
performed to determine the parents' level of under-
standing of their child's condition and offer appropriate
counseling and education. Based on the family's socio-
economic status and the status of the child, one must
evaluate the need for and availability of various social
services to provide respite and other supports.
13. Assessment of family resources should be per-
formed by social workers, psychologists, or other pro-
fessionals who specialize in families of autistic indi-
viduals, who may be better able to assess the family
dynamics in relation to parenting and behavior man-
agement strategies as they specifically relate to the
14. Level 2 Laboratory Evaluation may include
the following, as indicated:
(a). Metabolic testing or consultation is indicated
by a history of lethargy, cyclic vomiting, early seizures;
dysmorphic or coarse features; mental retardation or if
mental retardation cannot be excluded; if there is any
question concerning the occurrence or adequacy of new-
born screening for a birth within the US; or birth out of
the U.S. indicating the potential absence of newborn
screening and maternal public health measures.
As recommended by the American College of
Medical Genetics, selective metabolic testing should
be initiated by the presence of suggestive clinical and
(b). Genetic testing, specifically DNA analysis for
fragile X and high resolution chromosome studies (kary-
otype), are indicated for a diagnosis of autism, mental
retardation (or if mental retardation cannot be excluded),
if there is a family history of fragile X or undiagnosed
mental retardation, or if dysmorphic features are pres-
ent. It should be understood, however, that there is lit-
tle likelihood of positive karyotype or fragile X testing
is the presence of high-functioning autism.
If a family declines genetic testing, they should be
counseled to inform extended family members of the
potential genetic risks of this disorder so they may seek
appropriate genetic counseling.
Although there is no current method to detect
autism prenatally, parents of children with autism should
be counseled to inform them of the 50-fold increased
risk of having another autistic child (1 in 10 to 1 in 20,
as compared with 1 in 500 in the general population).
(c). Indications for a prolonged sleep-deprived
EEG with adequate sampling of slow wave sleep include
evidence of clinical seizures, history of regression
(clinically significant loss of social and communica-
tive function) at any age but especially in toddlers and
preschoolers, and in situations where there is a high
index of clinical suspicion that epilepsy, clinical or
subclinical, may be present. There is inadequate evi-
dence at the present time to recommend EEG studies
in all individuals with autism.
Other event-related potentials and magneto-
encephalography are considered research tools in the
evaluation of autism at the present time, without evi-
dence of routine clinical utility.
(d). Neuroimaging may be indicated by the pres-
ence of neurologic features not explained by the diag-
nosis of autism (e.g., asymmetric motor examination,
cranial nerve dysfunction, severe headache), in which
case the usual standards of practice apply. Routine
clinical neuroimaging does not have any role in the
Filipek et al.
diagnostic evaluation of autism at the present time,
even in the presence of autistic megalencephaly.
Functional imaging modalities (fMRI, SPECT, and
PET) at present are considered solely as research tools
in the evaluation of autism.
(e). Tests of unproven value: There is inadequate
evidence to support routine clinical testing of individu-
als with autism for hair analysis for trace elements, celiac
antibodies, allergy testing (in particular food allergies
for gluten, casein, Candida and other molds), immuno-
logical or neurochemical abnormalities, micronutrients
such as vitamin levels, intestinal permeability studies,
stool analysis, urinary peptides, mitochondrial disorders
(including lactate and pyruvate), thyroid function tests,
or erythrocyte glutathione peroxidase studies.
15. Reevaluation at least within a year of initial di-
agnosis and continued monitoring is an expected aspect
of clinical practice, because relatively small changes in
developmental level affect the impact of autism in the
16. It is the consensus of this Panel that the role of
medical professionals can no longer be limited to simply
the diagnosis of autism. Professionals must expand their
knowledge and involvement to be better able to counsel
families concerning available and appropriate treatment
modalities, whether educational, empirical, or "just off
the web." In addition, professionals must be familiar with
federal law which mandates a free and appropriate edu-
cation for all children from the age of 36 months, and in
some states, from zero to three as well.
1. Existing managed-care policy must change as
Extremely brief well-child visits must increase in
duration, with appropriate compensation, to permit the
implementation of routine developmental screening as
Short specialty visits must also increase in dura-
tion, with appropriate compensation, to permit the use
of appropriate diagnostic instruments, as recommended
Autism must be recognized as a medical disorder,
and managed care policy must cease to deny appropri-
ate medical or other therapeutic care under the rubric
of "developmental delay" or "mental health condition."
2. Existing governmental agencies that provide
services for individuals with developmental disabilities
must also change their eligibility criteria to include all
individuals on the autistic spectrum, whether or not the
relatively narrow criteria for Autistic Disorder are met,
who nonetheless must also receive the same adequate
assessments, appropriate diagnoses, and treatment op-
tions as do those with the formal diagnosis of Autistic
3. Public awareness and dissemination activities re-
garding the signs and symptoms of autism must occur
throughout communities, to provide information to par-
ents, child-care workers, health-care settings, and com-
munity centers. Small, attractive fliers targeting symp-
toms, needs, and outcomes of very young children and
also older children should be developed and disseminated
widely, in collaboration with the national autism soci-
eties and associations, schools, health, and allied health
agencies which need to join in this concerted effort.
4. Increased education of health-related and
education-related professionals about autism must occur
at the preservice level. Professionals must learn to pro-
vide more than a diagnosis and a telephone number for
governmental services to parents. Trainees in general
and developmental pediatrics, psychiatry, neurology,
early childhood education, speech and language pathol-
ogy, occupational therapy, physical therapy, psychology,
nursing, child-care providers, public health, education,
and other disciplines need markedly increased knowl-
edge about the range of symptoms of autism both early
and later in life, about the educational and community
needs of autistic individuals, and the potential outcomes
of autism. They must also learn how to discuss potential
risks of autism with families.
AN ANALYSIS OF DIFFERENCES RELATIVE
TO OTHER PRACTICE PARAMETERS
This consensus recommendation parallels and ex-
pands upon many of the major points of the Cure Autism
Now (CAN) Consensus Statement (CCS; Geschwind,
Cummings, & the CAN Consensus Group, 1998), espe-
cially its recognition of the effectiveness of appropriate
early intervention programs, the urgency of early iden-
tification and diagnosis of autistic spectrum disorders that
follows, and the necessity for a careful neurologic and
medical examination in all children with autism. Specific
recommendations regarding imaging, electrophysiology,
metabolic and genetic testing in this document are sim-
ilar to those from the CCS (Geschwind et al., 1998). The
purpose of the CCS was to provide guidelines for first
tier autism screening and diagnostic referral for primary
care practitioners (primarily pediatricians). The major
difference between the current recommendations and the
CCS is that the CCS recommended only the CHAT
(Baron-Cohen et al., 1992) as a rapid and effective
screening tool to screen all 18-month-old children for
autism, whereas in this current consensus, the CHAT is
Screening and Diagnosis of Autistic Spectrum Disorders
grouped along with other screening instruments, and is
felt not to be entirely sufficient for primary care screen-
ing purposes. Given the importance of early identifica-
tion, and the currently unacceptable delays that occur
between initial parental suspicion and diagnosis, the im-
portance of widespread developmental screening begin-
ning at 18 months cannot be overemphasized.
The American Academy of Child and Adolescent
Psychiatry (AACAP) Practice Parameters (Volkmar
et al., in press) were consulted in the development of
this document. The documents are similar with two main
differences due to the difference in scope of the two doc-
uments. The AACAP practice parameters are concerned
with aspects of diagnosis and treatment of particular rel-
evance to psychiatrists in their care for children, ado-
lescents, and adults with autism and related conditions.
The present document is concerned primarily with as-
pects of assessment, including diagnostic screening, and
does not address aspects of treatment. The AACAP looks
forward to continued participation in the effort to pro-
vide consensus practice parameters for autism.
The American Academy of Pediatrics (AAP) Com-
mittee on Children with Disabilities was consulted re-
garding its own development of a Policy Statement
regarding the role of the primary care pediatrician in the
diagnosis and management of children with autism,
which is in progress (American Academy of Pediatrics
Committee on Children with Disabilities, 1994). The
documents are also similar with main differences due to
differences in scope of the target audience. The AAP
document is concerned chiefly with the role of the pri-
mary care pediatrician and addresses management strate-
gies as well as early diagnosis.
RECOMMENDATION FOR PARAMETER
The Panel recommends review of these parame-
ters in 2 to 3 years.
would promote more positive long range outcomes for
individuals with autism.
2. Continue to study the usefulness of electro-
physiological techniques to clarify the role of epi-
lepsy in autism, especially in children with a history of
3. Continue efforts to identify contributing genes
to determine whether the behavioral syndromes which
constitute the basis of DSM-IV and ICD-10 have actual
4. Continue efforts to identify the harbingers,
causes, and outcome of autistic regression.
5. Attempt to identify environmental factors, such
as nonspecific infections or other immunologically me-
diated events, that might contribute to triggering the ex-
pression of autistic symptoms or regression.
6. Further research must focus on the development
and validation of appropriate tools to accurately assess
the cognitive and neuropsychological profile of indi-
viduals with autism, as it is clear that any of the cur-
rent available tools has, despite the benefits listed in
Table VI, significant limitations for use with autistic
7. A well-designed study of the prevalence of
EEG abnormalities and seizures, of MRI abnormalities,
and of genetic and metabolic abnormalities directly as-
sociated with autism.
8. Studies of the audiological characteristics of
autistic individuals and development of appropriate clin-
ical electrophysiological and behavioral procedures to as-
sess peripheral hearing sensitivity and suprathreshold re-
9. Further basic research on the development of
complex auditory processing in children, to provide in-
sight into the emergence of early auditory behaviors
10. Field trials on the results of implementing these
guidelines to determine who is identified diagnostically
by screening and the efficacy of the various screening
instruments in detecting autism at different ages.
RECOMMENDATIONS FOR FUTURE
1. Develop and validate appropriate screening
tools with adequate sensitivity and specificity for
autism in children prior to age 1 year, which could be
feasibly used by a wide range of practitioners. Current
evidence suggests that it is likely that many children
with autism can be identified by 12 to 18 months of
age. It is the consensus of this Panel that early recog-
nition can lead to early access to intervention, which
Contact Information for Recommended Instruments
Ages and Stages Ques-
Australian Scale for
Paul H. Brookes Publishing
PO Box 10624, Baltimore, Maryland
Telephone: 800-638-3775; Fax: 410-
Garnett, M. S., & Attwood, A. J.
(1998). The Australian Scale for
Asperger's Syndrome (pp.
17-19). In Attwood, T. (Ed.),
Filipek et al.
Autism Diagnostic Obser-
Checklist for Autism in
Asperger's Syndrome. A Guide
for Parents and Professionals.
London; Jessica Kingsley Pub-
lisher, ISBN 1853025771.
Department of Psychiatry, MC3077,
University of Chicago
5841 S. Maryland Ave, Chicago, IL
Telephone: 773-702-9707; Fax: 773-
Curriculum Associates, Inc.
P.O. Box 2001, North Billerica, MA
Telephone: 800-225-0248; Fax: 800-
Baron-Cohen, S. et al. (1992). Can
autism be detected at 18
months? The needle, the
haystack, and the CHAT. British
Journal of Psychiatry, 161,
Baron-Cohen, S. et al. (1996). Psy-
chological markers in the detec-
tion of autism in infancy in a
large population. British Journal
of Psychiatry, 168, 158-163.
Behavior Science Systems
Box 580274, Minneapolis, MN
Western Psychological Services
12031 Wilshire Boulevard
Los Angeles, CA 90025-1251
Telephone: 800-648-8857; Fax: 310-
Ellsworth and Vandermeer Press, Ltd.
4405 Scenic Drive, Nashville, TN
Telephone: 615-386-0061; Fax: 615-
Vanderbilt Child Development
Medical Center South, Room 426
2100 Pierce Avenue, Nashville, TN
Langley Porter Psychiatric Institute,
University of California, San Fran-
cisco, CA 94143-0984
Telephone: 415-476-7385; Fax: 415-
The authors express their gratitude to the follow-
ing people who contributed to this endeavor by their
Childhood Autism Rating
Parents' Evaluation of
The Parent Interview for
The Screening Tool for
Autism in Two-Year-
participation in the NIH State of the Science in Autism:
Screening and Diagnosis Working Conference, June
15-17, 1998: George Anderson, Anthony Bailey, W.
Ted Brown, Susan E. Bryson, Rebecca Landa, Jeffrey
Lewine, Catherine Lord, William Mcllvane, Sally
Ozonoff, Joseph Piven, Ricki Robinson, Bryna Siegel,
Vijendra K. Singh, Frank Symons, and Max Wiznitzer.
The current authors, participants and NIH Liaisons also
participated in this working conference.
The Panel acknowledges with gratitude the assis-
tance of Stephen Ashwal as the AAN-QSS Facilitator for
this project, the helpful consultations of Frances P. Glas-
coe, and Donald J. Siegel, and the assistance of Cheryl
Jess, Kerry E. Shea, and Jody Sallah in this endeavor.
This project was supported in part by HD28202/
HD27802/HD35458 (Filipek), HD35482 (Cook and
Volkmar), HD34565 (Dawson), HD36080 (Gravel),
HD3546a (Minshew), HD35468 (Rogers) and HD03008
(Volkmar) from the National Institute of Child Health
and Human Development; DC00223 (Gravel) from the
National Institute of Deafness and Communication Dis-
orders; MH01389/MH52223 (Cook), MH47117 (Daw-
son), and MH50620 (Stone) from the National Institute
of Mental Health; NS35896 (Filipek), NS33355 (Min-
shew), NS20489 (Rapin), from the National Institute of
Neurologic Disorders and Stroke, National Institutes of
Health, Bethesda, MD. This project was also supported
by MCJ-369029 (Accardo) from the Maternal and Child
Health Bureau, Health Resources and Services Admin-
istration, Department of Health and Human Resources.
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