J Neuropsychiatry Clin Neurosci 13:2, Spring 2001229
Validation of the Delirium
Comparison With the Delirium
Rating Scale and the Cognitive
Test for Delirium
Paula T. Trzepacz, M.D.
Dinesh Mittal, M.D.
Rafael Torres, M.D.
Kim Kanary, B.S.
John Norton, M.D.
Nita Jimerson, M.S.N.
patients, requires the use of valid rating scales and di-
agnostic criteria. Beginning with the DSM-III version of
the American Psychiatric Association’s diagnostic man-
ual in 1980, specific inclusion and exclusion criteria for
delirium became available. These were altered in sub-
sequent versions, DSM-III-R and DSM-IV. Although di-
agnostic criteria form a standard to ensure diagnosis of
the delirium syndrome, they do not provide for assess-
ment of symptom severity. Screening instruments to di-
agnose delirium, such as the Confusion Assessment
Method1and the Delirium Symptom Interview,2detect
some delirium symptoms but are not designed to mea-
sure symptom severity.
The Delirium Rating Scale (DRS)3is a widely used
delirium rating instrument that specifically, sensitively,
and reliably measures delirium symptoms as rated by a
psychiatrist or trained clinician.4,5The DRS is available
in French, Italian, Spanish, Dutch, Mandarin Chinese,
Korean, Swedish, Japanese, German, and Indian-lan-
Studies involving the DRS—reviewed elsewhere
through 19985—document its strengths and limitations.
Three of its items focus on features related todifferential
diagnosis (temporal onset of symptoms, fluctuation of
Received February 22, 2000; accepted July 21, 2000. From the Univer-
sity of Mississippi Medical Center and the Sonny Montgomery Vet-
erans Affairs Medical Center, Jackson, Mississippi; and the Eli Lilly
and Company, Neuroscience Research, U.S. Affiliate, Indianapolis,In-
diana. Address correspondence to Dr. Trzepacz, Lilly Corporate Cen-
ter, drop code 4133, Indianapolis, IN 46285. E-mail: PTT@lilly.com.
Copyright ? 2001 American Psychiatric Publishing, Inc.
The DRS-R-98, a 16-item clinician-rated scale
with 13 severity items and 3 diagnostic items,
was validated against the Cognitive Test for De-
lirium (CTD), Clinical Global Impression scale
(CGI), and Delirium Rating Scale (DRS) among
five diagnostic groups (N?68): delirium, demen-
tia, depression, schizophrenia, and other. Mean
and median DRS- R-98 scores significantly
(P?0.001) distinguished delirium from each other
group. DRS-R-98 total scores correlated highly
with DRS, CTD, and CGI scores. Interrater reli-
ability and internal consistency were very high.
Cutoff scores for delirium are recommended based
on ROC analyses (sensitivity and specificity
ranges: total, 91%–100% and 85%–100%; sever-
ity, 86%–100% and 77%– 93%, respectively, de-
pending on the cutoffs or comparison groups cho-
sen). The DRS-R-98 is a valid measure of
delirium severity over a broad range of symptoms
and is a useful diagnostic and assessment tool.
The DRS-R-98 is ideal for longitudinal studies.
(The Journal of Neuropsychiatry and Clinical
Neurosciences 2001; 13:229–242)
esearch on delirium, an acute confusional state that
affects on average about 20% of general hospital
230J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
symptoms, and physical etiology) and add tospecificity,
but are not easy to rate repeatedly during serial admin-
istrations within an episode of delirium. Some research-
ers have solved this problem by modifying the DRS into
a 7- or 8-item scale after the initial administration. The
DRS item for psychomotor behavior combines hypoac-
tivity and hyperactivity, thereby limiting its usefulness
in assessing motor subtypes of delirium. Various cog-
nitive deficits are combined into one item because sepa-
rate bedside cognitive tests were originally suggestedas
adjuncts to the DRS. However, not having a separate
item for attentional deficits makes it difficult to study
attention’s presumed cardinal role in delirium or what
symptoms constitute “clouding of consciousness.” The
lack of items for language impairment or thought pro-
cess abnormalities limits study of what actually contrib-
utes to “confusion” other than cognitive deficits. Thus,
the DRS has some limitations for useinphenomenologic
and longitudinal treatment research.
Our revision of the DRS was intended to address
these shortcomings of the original scale. The revision
includes two sections: three diagnostic items for initial
ratings and a 13-item severity scale that is used for re-
phasize gradations of symptom intensity; specific char-
acteristics can be noted on the score sheet. Items cover
language, thought processes, two motoric presentations,
and five components of cognition. Neither the DRS nor
its revision is intended to assess stupor or coma.
The intent of this study was to 1) validate the Delir-
ium Rating Scale- Revised-98 (DRS-R-98), 2) establishits
reliability, as well as its sensitivity and specificity for
distinguishing delirious from nondelirious psychiatric
groups, and 3) assess its ability to function as a severity
measure of delirium. It was compared with the DRS, the
Cognitive Test for Delirium (CTD), and a global clinical
Adult subjects were recruited from medical, surgical,
psychiatric, rehabilitation, and nursing home care in-
patient units of the University of Mississippi Medical
Center affiliated hospitals over a 5-month period in
1999. We recruited delirious, demented, schizophrenic,
depressed, and other psychiatric patients to form the
five different comparison groups. Verbal assent to be
interviewed was used to determine participation in this
study as approved by the University of Mississippi
Medical Center institutional review board. There were
no exclusion criteria except an unwillingness to be psy-
chiatrically assessed. Subjects were evaluated on the
hospital unit cross-sectionally, except for a few delirious
subjects who were retested after their delirium im-
proved. Demographic data were obtained from the pa-
tient, chart, staff, and/or family and friends.
Evaluations were done according to the availability of
raters in a quasi-randomized fashion. The researchteam
contacted the relevant service and requested a list of
patients who could be approached for inclusion in the
study. DRS and DRS-R-98 ratings were done blind to
diagnosis by the study psychiatrists, who were trained
to use these instruments. The research assistants
screened cases for suitability. Ratings made use of in-
formation from all available sources, including discus-
sions with caregivers or visitors to obtain information,
as well as limited chart review under supervision of the
research assistant or referring physician to maintain
blindness to diagnosis. Delirium scale ratings covered a
Psychiatric diagnoses were made by the referring ser-
vice physician using DSM-IV criteria and all available
usual clinical information to finalize the diagnosis. The
referring physician also completed the Clinical Global
Impression (CGI) scale for overall severity of illness, un-
der instructions to compare the subjects with other pa-
tients having that same disorder. No particular training
was done for completion of the CGI. CGI ratings were
used to compare illness severity between groups and to
correlate with delirium scale ratings within the delirium
Interrater reliability for the DRS-R-98 was established
by using a subset of subjects representing various di-
agnostic groups. Researchpsychiatrists(P.T.,D.M.,R.T.)
independently rated the same subjects following a sin-
gle interview when they were blind to diagnosis, and
comparisons were made between pairs of raters.
Construct validity was established mostly by com-
paring the DRS-R-98 with the DRS and to a lesser extent
by comparing it with the CTD. Sensitivity and specific-
ity of the DRS-R-98 were determined by comparing
scores from delirious subjects with other diagnostic
groups’ scores. This comparison also assisted with eval-
uating criterion validity.
The DRS is a 10-item clinician-rated scale with a maxi-
mum possible score of 32 points. Items represent symp-
toms that are rated on a scale of 0 to 2, 3, or 4 points,
with text descriptions for each point. The items are tem-
poral onset of symptoms, perceptual disturbances, hal-
lucination type, delusions, psychomotor behavior, cog-
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001231
TRZEPACZ et al.
nitive status during formal testing, physical disorder,
sleep-wake cycle disturbance, labilityofmood,andvari-
ability of symptoms. The DRS has good scale character-
istics based on a number of studies of delirious popu-
lations. Its interrater reliability (intraclass correlation
coefficients) ranges from 0.86 to 0.97 for psychiatric or
geriatric physicians and 0.59 to 0.99 for nonphysicians;
specificity ranges from 0.82 to 0.94, sensitivity from 0.82
The DRS-R-98 is a 16-item scale (see Appendix A)
with a maximum total scale score of 46 points (includes
the three diagnostic items) and a maximum severity
score of 39 points. Whenever an item of the DRS-R-98
could not be rated—which was usually dependent on
the degree of cooperation—it was so noted and later
scored midway, that is, as 1.5 points; this occurred
rarely. We used three words to assess short-term mem-
ory, months of the year backwardstohelprateattention,
copying intersecting pentagons and drawing a clockface
to help assess visuoconstructional ability, and parts of a
pen and/or watch to assess naming.
Each subject was administered the Cognitive Test for
Delirium6by a research assistant as a brief, broad mea-
sure of cognitive function. The CTD was designed spe-
cifically for delirious patients, especially those who can-
not speak. It tests orientation, attention, visual memory,
and conceptual reasoning and has been shown to cor-
relate highly with the Mini-Mental State Examination
(MMSE) in delirious patients. A suggested cutoff score
for delirium is ?19 points.
The CGI is scored as a single overall impression of
illness severity on a Likert-type scale ranging from 1 to
7 points.7It was used to grossly measure severity of ill-
ness within diagnostic groups. Unlike the other scales,
the CGI was completed without prior training by a va-
riety of treating physicians over a broad range of clinical
Data were analyzed by using SPSS-PC software. Age
and rating scale data were expressed as means and stan-
dard deviations. Statistical significance was set at
P?0.05. DRS and DRS-R-98 scores from the primary
rater were used for all analyses (except in calculating
interrater reliability when pairs of raters were used).
Age was correlated with total rating scalescoresforeach
diagnostic group by Pearson correlation. Chi-square
was used to compare race and sex among groups.
DRS-R-98 total scores were compared with both the
DRS and the CTD in delirious subjects, using a Pearson
correlation to assess construct validity and ability to as-
sess severity over a range of impairment levels. Scores
for each DRS-R-98 item were correlated with DRS-R-98
total scale scores, using Cronbach’s alpha coefficient to
assess internal consistency of the scale as a measure of
delirium. To assess empirical validity of the DRS-R-98
as a delirium scale, total and severity scores were com-
pared among the five diagnostic groups by one-way
analysis of variance (ANOVA), with post hoc pairwise
comparisons to determine where the differences lie.
Boxplots were graphed to show medians and distri-
butions of rating scale and CTD scores for each diag-
nostic group. The Kruskal-Wallis test was performed to
assess for between-group difference.
DRS-R-98 scores were compared with “after usual
treatment” scores by use of paired t-tests in a subset of
delirious subjects to assess the DRS-R-98 as a severity
scale over time. Total scores were correlated with CGI
scores as another way to assess DRS-R-98 as a severity
Cutoff scores for the DRS-R-98 were determined by
using receiver-operator characteristic (ROC) analyses to
determine acceptable levels of sensitivity and specificity
when comparing the delirium group either with the de-
mented group or with all nondelirious subjects.
CGI scores were compared between groups by using
one-way ANOVA to assess whether illness severity was
similar among diagnostic groups.
Interrater reliabilities for the DRS-R-98 and DRS total
scores were measured by using an intraclass coefficient
for pairs of independent raters.
A total of 68 subjects were evaluated from five diagnos-
tic groups: 24 delirious, 13 demented, 9 schizophrenic,
12 depressed, and 10 “other.” Twenty-seven were re-
cruited from medical-surgical units, 17 from a medical-
psychiatric unit, 15 from general psychiatric units, 4
from a nursing home unit, and 5 from a rehabilitation
Table 1 describes demographic characteristics of sub-
jects for each diagnostic group. There were no signifi-
cant differences among groups for race,where56%were
white, 42% black, and 3% other (1 Hispanic and 1 Choc-
taw Native American). There were 51 males and 17 fe-
males (because of the inclusion of a Veterans Affairs
Medical Center population) but no difference in gender
or race ratios among groups. Mean age was significantly
different between groups (F?7.43, df?4,63, P?0.001),
as might be expectedfromthedifferentagedistributions
of the illnesses studied. Schizophrenic subjects weresig-
nificantly younger than delirious (P?0.01) or demented
subjects (P?0.001), and “other” subjects were signifi-
232 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
TABLE 2. Rating scale scores in five diagnostic groups, mean?SD (range)
Scale Deliriuma(n?24) Dementia (n?13) Schizophrenia (n?9) Depression (n?12) Other (n?10)
was 67 because an ‘‘other’’ case had a missing CTD score and a ‘‘depression’’ case had a missing DRS score. DRS?Delirium Rating Scale;
DRS-R-98?Delirium Rating Scale-Revised-98; CTD?Cognitive Test for Delirium; CGI?Clinical Global Impression.
aIncludes 2 subjects whose delirium was resolving.
*One-way analysis of variance, P?0.001 among groups.
**One-way analysis of variance, P?0.012 among groups.
Groups are defined in the notes to Table 1. The total subjects compared for each scale was 68 except DRS and CTD, where it
TABLE 1.Demographics for five diagnostic groups
a2 Alzheimer’s, 2 vascular, 1 human immunodeficiency virus–type 1 infection with cryptococcus, 8 dementia not otherwise specified (NOS).
b5 undifferentiated schizophrenia, 2 paranoid schizophrenia, 1 schizoaffective (manic type), 1 psychosis NOS.
c9 major depression (4/9 with psychotic features), 1 depression NOS, 1 bipolar depressed.
d2 alcohol dependence, 3 cognitive disorder NOS, 1 amnestic disorder, 2 opioid dependence, 1 adjustment disorder depressed, 1 delirium
cantly younger than demented subjects (P?0.01). All
groups had a broad range in age except the demented
subjects, who were all over 60 years old.
Table 2 shows mean scores and standard deviations for
each group for DRS, DRS-R-98 total, DRS-R-98 severity,
CTD, and CGI. There was a highly significant difference
among diagnostic groups for the CTD (F?19.3,
df?4,62, P?0.001), DRS-R-98 total scale (F?47.9,
df?4,63, P?0.001), DRS-R-98 severity scale (F?35.0,
P?0.001). The CGI also distinguished the groups
(F?3.5, df?4,63, P?0.01). Delirium subjects had the
highest mean scores on the delirium rating scales and
the lowest scores on the CTD compared with any di-
agnostic group, indicating they had more delirium
symptoms and cognitive impairment.
ANOVA pairwise comparisons showed that themean
DRS score was significantly higher in the delirium
group compared with each of the other groups
(P?0.001). The DRS did not differ among dementia,
schizophrenia, depression, or “other” groups.
With pairwise comparisons, the mean DRS-R-98 total
score was significantly higher in the delirium group
compared with each of the other groups (P?0.001). The
DRS-R-98 total score did not distinguish schizophrenia,
depressed, or “other” groups from one another, nor did
it distinguish dementia from the “other” group. How-
ever, it did distinguish dementia from schizophrenia
and depressed groups (P?0.05).
Pairwise comparisons showed that the mean DRS-R-
98 severity score was significantly higher inthedelirium
group compared with each of the other groups
(P?0.001). It distinguished dementia from both depres-
sion and “other” groups (P?0.05), but not from schizo-
phrenia. Like the DRS-R-98 total scale, it did not differ
among “other,” schizophrenia, and depression groups.
Pairwise comparisons showed that mean CTD scores
were significantly lower in the delirium group than in
any other group at P?0.001, except for dementia at
P?0.05. The CTD did not distinguish the schizophrenic
group from any group except delirium, but it did dis-
tinguish dementia from the depressed and “other”
Pairwise comparisons showed that mean CGI scores
were not significantly different among any groups ex-
cept between delirium and “other,” where the latterwas
less impaired than the delirium group (P?0.03). The
mean CGI score was in the “moderately to markedly
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001 233
TRZEPACZ et al.
impaired” range for all groups except for “other” which
was halfway between “mildly” and “moderately” im-
paired. This indicates that the major diagnostic groups
were well matched for breadth of overall illnessseverity
levels based on a clinical global impression.
In addition to comparing group means, we graphed
boxplots (Figure 1) to show the distribution of scale
scores in quartiles (middle 50% in the box) and median
scores (in solid black lines). On Kruskal-Wallis compar-
isons, scores were significantly different among groups
(P?0.001) for the DRS, DRS-R-98 total and severity, and
CTD scales. Median scores and middle quartiles for de-
lirious subjects did not overlap with those from any
other group on any scale, except for the dementia group
on the CTD, suggesting that the CTD is less discrimi-
nating. The DRS distribution shows very little overlap
between delirium and any other group except between
its lower quartile and the upper quartile of the dementia
and “other” groups. One severely impaired schizo-
phrenic outlier and one severely psychotically de-
pressed outlier just reached the lowest distribution of
the DRS range, as well as one “other” patient who had
a recently resolved delirium.
The most overlap on boxplots for DRS-R-98 total or
severity scores occurs between the lower quartile of the
delirium group and the dementia group, with somewhat
a resolving delirium group outlier. CTDscoresarelowest
in the delirium group, but the boxes for delirium and
dementia groups overlap, and 2 schizophrenic outliers
CGI) overlap with the delirium box.
Two subjects in the delirium grouphad beendelirious
for a while and were improving, and one subject in the
“other” group had a brief nocturnal delirium that was
mostly resolved by morning when he was rated. Be-
cause of their varying degrees of resolving status, these
3 subjects were analyzed separately against the other 22
milder status. Compared with subjects having full-
blown delirium, those with resolving delirium had sig-
nificantly higher mean scores on the CTD (23.7?2.5 vs.
10.9?5.7; t??3.7, df?23, P?0.001), and significantly
lower on the DRS (10.3?2.3 vs. 19.3?4.8; t?3.1, df?23,
P?0.005), on the DRS-R-98 total (13.0?2.0 vs. 28.2?5.4;
t?4.8, df?23, P?0.001) and on the DRS-R-98 severity
(7.3?1.5 vs. 22.6?4.9; t?5.3, df?23, P?0.001). There
was no difference in age between those with resolving
and those with more full-blown delirium.
DRS-R-98 Characteristics in Delirious Subjects
Correlations were performed between rating scales in
the delirium group to address validity of the DRS-R-98.
Age did not correlate with any measure. The DRS cor-
related strongly with the DRS-R-98 total (r?0.83,
P?0.001) and DRS-R-98 severity (r?0.80, P?0.001) sug-
gesting the newer scale is a good measure of delirium.
As would be expected, the DRS-R-98 total score corre-
lates very strongly with the DRS-R-98 severity score
(r?0.99, P?0.001). Both the DRS and the DRS-R-98 cor-
related somewhat less strongly with the CTD(r??0.41,
P?0.05 for the DRS; r??0.62, P?0.001 for the DRS-R-
98 total; and r??0.63, P?0.001 for DRS-R-98 severity),
consistent with the delirium scales measuring symp-
toms more broadly than just cognition. Correlations
with the CGI were strong but less so than between the
two delirium rating scales with each other (r?0.45,
P?0.05 for DRS; r?0.62, P?0.001 for DRS-R-98 total;
and r?0.61, P?0.001 for DRS-R-98 severity), likely re-
flecting the CGI’s more nonspecific, global nature.
DRS-R-98 Pre and Post Treatment
Six of the delirious subjects were reassessed after treat-
ment when they no longer met DSM-IV criteria for de-
lirium. Their mean age was 55.3?23.1 years (range 18–
82). Their mean scores for CTD, DRS,DRS-R-98severity,
and CGI are listed in Table 3. There were significant
improvements on all measures after treatment. In par-
ticular, the DRS-R-98 severity scale improved from a
mean of 21.5?5.6 points to 5.2?3.5 (t?7.13, df?5,
P?0.001), indicating an ability to measure change in
clinical status in parallel to global clinical, cognitive,and
diagnostic assessments. The DRS also declined from a
mean score of 18.3?3.9, clearly in the delirious range,
to 3.5?2.1 (t?10.6, df?5, P?0.001), clearly out of the
delirious range. CGI improved significantly from
“moderate/marked impairment” to “much/very much
improved” (t?6.3, df?5, P?0.001). Although the delir-
ium rating scale raters were aware of the delirium diag-
nosis at the second rating, the CGI was rated indepen-
dently by the primary treating physician and the CTD
was administered and scored by a research assistant.
The Cronbach’s alpha coefficient in the delirium group
was 0.90 for the DRS-R-98 total scale and 0.87 for the
DRS-R-98 severity scale, supporting the reliability of the
scale and its internal consistency. In addition, when the
effect of each individual item wasdeletedfromthescale,
coefficients ranged from 0.88 to 0.90 for the DRS-R-98
total and from 0.84 to 0.87 for the DRS-R-98 severity
scale, suggesting a high degree of internal consistency
among items of the scale. Table 4 lists alpha coefficients
for both the DRS-R-98 total and DRS-R-98severityscales
as each item is removed from the scale. The DRS also
234 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
FIGURE 1. Boxplots of DRS, DRS-R-98 Total, DRS-R-98 Severity, and CTD scores for each of the five diagnostic groups. Median scores
are denoted by the solid line within the boxes. The boxes represent the middle 50% of the scores. Outliers are denoted by
open circles. DRS?Delirium Rating Scale; CTD?Cognitive Test for Delirium.
Total DRS Score
Total CTD Score
9 24 139 11
N =N =
DRS-R-98 Severity Score
showed a high alpha coefficient(0.87),rangingfrom0.83
to 0.87 when each item was removed, reflective of its
high internal consistency.
Three trained psychiatrist raters were used to calculate
an intraclass correlation coefficient (ICC) for the DRS
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001235
TRZEPACZ et al.
TABLE 4. Alpha coefficients for DRS-R-98 total and DRS-R-98
severity scales when each item is removed from the
Sleep-wake cycle disturbance
Perceptions and hallucinations
Lability of affect
Thought process abnormalities
Temporal onset of symptoms
Fluctuation of symptom severity
DRS-R-98?Delirium Rating Scale-Revised-98; N/A?not
TABLE 3.Pre/post treatment scores (mean?SD) in a delirium
Scale-Revised-98; CTD?Cognitive Test for Delirium; CGI?Clinical
* Paired t-tests, P?0.001.
**Paired t-test, P?0.01.
DRS?Delirium Rating Scale; DRS-R-98?Delirium Rating
and DRS-R-98. When the primary rater was compared
with the secondary rater for the DRS (n?25), ICC?0.99;
for the DRS-R-98 total (n?26), ICC?0.98; and for the
DRS-R-98 severity (n?26), ICC?0.99. When each com-
bination of pairs of raters was compared for each rating
scale, the ICCs ranged from 0.98 to 0.99 (10 or 11 cases
were used for each rater pair comparison).
Sensitivity and Specificity
Results of receiver operating curve (ROC) analyses are
shown in Table 5.
ROC analyses were performed for DRS-R-98 scores
comparing the delirium group versus all other diagno-
ses, as well as the delirium group versus only dementia
(dementia being the more likely diagnostic confound).
When delirium was compared with all other groups for
the DRS-R-98 total scale, cutoff scores of 15.25 and 17.75
were chosen as the two best options, resulting in the
same sensitivity (92%), but the higher cutoff had a
higher specificity (95%). The best cutoff score for the
DRS-R-98 severity scale was 15.25, resulting in 92% sen-
sitivity and 93% specificity.
The delirium group was then compared only with the
dementia group, and the best cutoff scores (17.75 for
total and 15.25 for severity) resulted in 92% sensitivity
for both of the DRS-R-98 scales but a higher specificity
for the total scale (85%) than for the severity scale (77%).
On the basis of clinical experience, diagnostic items are
expected to have less overlap between delirium and de-
mentia than other symptoms.
A separate ROC analysis was performed that ex-
cluded the two resolving delirium subjects because they
had significantly lower DRS-R-98 scores (see above)
than other delirium subjects and would be expected to
affect discrimination between groups. At the cutoff of
17.75, the DRS-R-98 total scale sensitivity increased to
100%, and higher cutoffs (21.5 and 22.5) each resulted
in a somewhat lower sensitivity (91%) but increased
specificities (92% and 100%, respectively). On the DRS-
R-98 severity scale with a cutoffscoreof15.25,excluding
these two subjects resulted in an increased sensitivity of
100% with the same specificity (77%), whereas raising
the cutoff score to 17 reduced the sensitivity and in-
creased the specificity.
We describe a new delirium symptom rating scale, the
DRS-R-98, that was substantially revised from the origi-
nal scale, the DRS. We present data to show that this
new scale functions reliably and validly both as a se-
verity scale for repeated measurements and as a total
scale that includes diagnostic items, by studying it in
comparison to four other diagnostic inpatient groups
whose illness severity was comparable to that of the de-
lirium group. The DRS-R-98 is designed to measure a
breadth of delirium symptoms, using phenomenologi-
cal items common to psychiatric practice without mak-
ing assumptions about what comprises certain domains
as cited elsewhere in the literature—for example,
“clouding of consciousness,” “confusion,” “incoher-
ence,” or “psychomotor behavior.” By assessing purer
symptoms individually, researchers can more accu-
rately describe delirium, how its symptoms evolve dur-
ing an episode and respond to treatment, and which
symptoms might represent core symptoms or cluster
into syndrome subtypes. In addition, the 13-item sever-
ity scale is more easily repeated at shorter intervals for
treatment studies or to elucidate what symptom
236 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
TABLE 5. Sensitivity and specificity based on ROC analysis
Sensitivity Comparison GroupsCutoff ScoreSpecificity Cutoff ScoreSpecificity
Delirium vs. dementia
Delirium vs. dementiaa
Delirium vs. all other groups15.25 9293
aWhen two cases of ‘‘delirium resolving’’ were removed from the ‘‘delirium’’ group.
ROC?receiver-operator characteristic; DRS-R-98?Delirium Rating Scale-Revised-98.
changes constitute thecharacteristicwaxingandwaning
of delirium during a 24-hour period.
The DRS-R-98 appears to be a valid measure of delir-
ium. We analyzed its characteristics for both the total
scale and the severity scale. The DRS-R-98 correlated
highly with scores on the DRS and the CTD in delirious
subjects. Its mean and median scores were significantly
higher in delirium subjects than in any of itscomparison
“other.” These patient groups were well matched for
illness severity; such matching is especially important
when comparing dementia and delirium groups. There
was little overlap in the boxplot distribution of DRS-R-
98 scores in the delirium group compared with other
diagnostic groups, although the DRS-R-98 total scale
had less overlap with other diagnostic groups than did
the severity scale, as would be expected.
Cronbach’s alpha coefficient was high (0.90), indicat-
ing high internal consistency among its 16 items; this
level of consistency was largely maintained for the se-
verity scale alone (0.87). Each item also individually
contributed strongly to the scale. Interrater reliability
was excellent among pairs of three psychiatrist raters
doing independent ratings during a single clinical in-
The DRS-R-98 was compared with the CTD instead of
the MMSE because the CTD was designed for delirium
and can be administered to nonverbal or intubated pa-
tients. Also, the CTD has the advantage of assessing
some executive and more nonverbal cognitive functions
of the nondominant hemisphere, which complements
the verbal modalities we used during administration of
the DRS-R-98. Despite this difference, the two scalescor-
related highly. In addition, two recent studies8,9that re-
lied on cognitive tests to assess delirium found high dis-
criminating ability of the items measuring functions of
the nondominant hemisphere, in keeping with the neu-
roanatomical hypothesis that the right-sided neural
pathways, often under-studied, are integral to delirium
Subjects with resolving delirium were included in the
delirium group for all analyses, but these subjects had
less impairment on scale measurements, and their data
affected the cutoff when delirium was compared with
dementia. In clinical practice when such cases will be
assessed, the differential from dementia will depend in
part on taking a careful history. Focusing on just the
DRS-R-98 diagnostic items may assist in this process. A
different study using the DRS to compare delirious and
delirious-demented elderly subjects found that delirium
symptoms largely overshadowed dementia symptoms,
although there were still some differences.4Longitudi-
nal testing of the DRS-R-98 in delirious-demented pa-
tients whose delirium resolves will be needed to deter-
mine which items best distinguish these groups.
In our study the CTD was less robust in distinguish-
ing dementia from delirium, and many in our dementia
group scored lower than the cutoff score of 19 points
recommended in Hart and colleagues’ original report.6
Our dementia group had a CTD mean score of about 18
and showed more overlap with the delirium group on
boxplots than did the DRS or DRS-R-98. This is likely
because the CTD measures only one dimension of de-
lirium phenomenology, unlike these broader symptom
Two delirium severity rating instruments have been
published in recent years. The Confusional State Eval-
uation (CSE)12is a three-part,22-itemscalefromSweden
that was tested only in delirium patients (Nrangedfrom
28 to 51 patients). Thus, no comparison was made with
dementia patients, nor were sensitivity and specificity
values obtainable. In addition, patients with comorbid
dementia were included in the delirium group, which
significantly confounds phenomenologic validity of the
scale as a delirium assessment tool. Dementia patients
have different symptom severity even for someoverlap-
ping symptoms.13,14O’Keefe’s Delirium Assessment
Scale (DAS)15used operationalized DSM-III criteria to
compare delirious, delirious-demented, demented, and
not cognitively impaired groups (N?48). Sensitivity
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001 237
TRZEPACZ et al.
ranged from 83% to 88% and specificity from 79% to
88% for delirium diagnosis, and interrater reliability
ranged from 0.66 to 0.99. Onset of symptoms was not
specifically rated, but was arbitrarily scored as acute.
Three recent delirium studies have used only cogni-
tive tests to assess delirium.9,16,17Hart et al.9used a step-
wise discriminant analysis of CTD item scores to deter-
mine that an abbreviated version using 2 of 9 items—
visual attention span and recognition memory for pic-
tures—discriminated 19 delirium patients in the inten-
sive care unit from other diagnostic groups with high
reliability (alpha?0.79). Bettinetal.17foundcorrelations
of about 0.50 betweencognitivetests(forwarddigitspan
and similarities) and expert serial ratings using DSM-
III-R in 22 delirious and 15 control elderly subjects.
These investigators felt that backward digit span had a
floor effect but recommended forward digit span for
monitoring symptom severity in delirium. However,
O’Keefe and Grosney16found that forward digit span
did not distinguish delirium from dementia patients,
suggesting that this test would be inadequate in clinical
situations. Further, they found that a global rating of
attentiveness, digit span backwards, and a cancellation
test distinguished delirium from dementia, but that the
MMSE and a vigilance test did not. However, they ex-
cluded anyone with an MMSE score ?10, which may
have biased the results away from more severe delirium
cases. Also, 4 of 18 delirium subjects had comorbid de-
mentia. Although the use of such tests is clinically ex-
peditious, it is unlikely that cognitive tests alone can
adequately capture the breadth of symptoms needed to
assess delirium severity and distinguish delirium from
In summary, the DRS-R-98 is a valid and reliable
symptom severity scalefordeliriumthathasadvantages
over the original DRS for flexibility and breadth of
symptom coverage. It is the only validated delirium rat-
ing instrument with sufficient breadth and detail for use
in phenomenology and in longitudinal studies of delir-
ium patients, including serial measurements in treat-
ment research. Moreover, unlike most other deliriumin-
struments, it was validated against a dementia group
and other psychiatric diagnostic groups. It is currently
being translated into other languages. Further research
using the DRS-R-98 is needed to extend and replicate its
utility, including longitudinal comparisons of condi-
tions that can occur comorbidly with delirium.
The authors thank Robert W. Baker, M.D., Andrea F.
DiMartini, M.D., James Levenson, M.D., Roos van derMast,
M.D., Ph.D., and Angelos Halaris, M.D., Ph.D. fortheircon-
tributions to scale development; Joel Greenhouse, Ph.D., for
statistical consultation; and Henry Nasrallah, M.D., and
Gurdial Sandhu, M.D., for their support during this study.
This work was supported in part by the Mental Illness Re-
search Education and Clinical Center, Veterans Integrated
Service Network 16 (MIRECC-VISN 16), Department of
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238 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
APPENDIX A. The Delirium Rating Scale-Revised-98
GENERAL INSTRUCTIONS FOR USE OF THE DRS-R-98
The Delirium Rating Scale-Revised-98 (DRS-R-98) is a 16-item clinician-rated scale with two sections and a score sheet.
The 13-item severity section can be scored separately from the 3-item diagnostic section; their sum constitutes the total scale
score. The severity section functions as a separate scale for repeated measures at short intervals within an episode ofdelirium.
The total scale can be scored initially to enhance differential diagnosis by capturing characteristic features of delirium, such
as acute onset and fluctuation of symptom severity. Concomitant use of diagnostic criteria such as from the International
Classification of Disease (ICD)-10 Research Manual or versions of the Diagnostic and Statistical Manual (DSM) will enhance
its ability to measure delirium when demented patients are involved because the DRS-R-98 is mostly a severity scale.
All items are anchored by text descriptions as guides for rating along a continuum from normal to severely impaired.
Severity items are rated from 0 to 3 points and diagnostic items from 0 to either 2 or 3 points. The scoresheet offers space
to circle item ratings and to optionally note characteristics of symptoms (e.g., type of hallucination) or the condition of
patients during the ratings (e.g., restrained).
Though designed to be rated by psychiatrists, other physicians, nurses, and psychologists can use it if they have had
appropriate clinical training in evaluating psychiatric phenomenology in medically ill patients. It can be used in research
or comprehensive clinical evaluations. It does require enough clinical expertise to distinguish, for example, language
problems from thought process abnormalities or delusions from confabulation. Even with sufficient clinical expertise, at
times it may be difficult to make certain distinctions and more thanone itemmay needtoberatedtoreflectthatpresentation
(e.g., Wernicke’s aphasia and severe loose associations).
The DRS-R-98 can be used in conjunction with the Delirium Rating Scale (DRS) for certain research purposes becausethey
differ substantially in descriptions of items. For example, the DRS may be more helpful for patients emerging from stupor.
The DRS-R-98 measures symptoms without regard to cause. Thus, preexisting conditions may add points, for example,
dysphasia will affect the language item. However, longitudinal ratings will clarify effects of preexisiting conditions after
the delirium has cleared. The inclusion of mentally retarded and Cognitive Disorder Not Otherwise Specified subjects
during the validation study suggests that delirium can still be reliably assessed in the presence of such confounds.
All sources of available information are used to rate the patient—family, visitors, hospital staff, doctors, medical chart,
and so on. Even a hospital roommate can contribute information. During interviews for such collateral information,ensure
that terms used are mutually understood before accepting others’ interpretation of symptoms.
Any time frame can be chosen for the DRS-R-98. Time frames greater than 24 hours are probably not necessary as this
coincides with circadian rhythms and their possible disruptions. Shorter periods (e.g., 4 to 12 hours) may be helpful for
intervention assessment—either for clinical or research purposes—though the fluctuating nature of symptom severity may
need to be considered when interpreting the scores. Choosing periods less than 2 hours risks not adequately capturing
some items (e.g., hallucinations, sleep-wake cycle disturbance) that occur intermittently. Insuchcircumstances,aresearcher
may wish to use a smaller subset of items to monitor the patient, though such a subscale has not been validated.
Some items are rated based on examination and history, while others incorporate formal testing (e.g., cognitive and
language items). It may be useful for a given clinician to standardize the questions used routinely in his/her practice, for
example, asking months of the year backwards for attention, clockface or puzzle pieces for visuospatial ability, and par-
ticular items for confrontational naming. Adjunctive use of the Cognitive Test for Delirium (CTD) or some of its items
offers the advantage of not needing the patient to write or speak. Evaluation of general information included in the long-
term memory item should be geared appropriately to the educational and cultural background of the patient.
When both interview behavior and formally elicited responses are used, the relative contribution of each needs to be
weighed by the clinician and a scoring judgment needs to be made. For example, on the attention item a patient has difficulty
with reciting months of the year backwards but attends fairly well during the interview, or on long-term memory a patient
recalls personal remote information accurately, but cannot recall well on formal testing of three words after 15 minutes.
Despite text descriptions for each item rating, the rater may need to exercise judgment in scoring. At times an inter-
mediate rating with a 0.5 point interval may be needed (e.g., 2.5 points) if the rater cannot decide between two choices.
Also, the time frame chosen may affect how to weigh the presence of certain symptoms. For example, a patient who has
periods of intense hyperactivity and hypoactivity in a 24-hour period would be rated as “3” on both items #7 and 8. If this
same patient is rated for a shorter interval that only involved hyperactivity, then item #7 would be rated as “3” and item
#8 would be “0”.
In cases where an item cannot be rated at all, the rater should make a notation on the score sheet and decide later how
to handle that item’s scoring. If used for research, a statistical consultant may have to advise. If used clinically, altering the
denominator of the maximum possible score may be acceptable.
? Trzepacz 1998
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001 239
TRZEPACZ et al.
DELIRIUM RATING SCALE-R-98 (DRS-R-98)
This is a revision of the Delirium Rating Scale (Trzepacz et al. 1988). It is used for initial assessmentand repeatedmeasurementsofdelirium
symptom severity. The sum of the 13 item scores provides a severity score. All available sources of information are used to rate the items
(nurses, family, chart) in addition to examination of the patient. For serial repeated ratings of delirium severity, reasonable time frames
should be chosen between ratings to document meaningful changes because delirium symptom severity can fluctuate without interven-
DRS-R-98 SEVERITY SCALE
Rate sleep-wake pattern using all sources of information, including from family, caregivers, nurses’ reports, and patient. Try to distinguish
sleep from resting with eyes closed.
Sleep-wake cycle disturbance
Mild sleep continuity disturbance at night or occasional drowsiness during the day
Moderate disorganization of sleep-wake cycle (e.g., falling asleep during conversations, napping during the day or several brief
awakenings during the night with confusion/behavioral changes or very little nighttime sleep)
Severe disruption of sleep-wake cycle (e.g., day-night reversal of sleep-wake cycle or severe circadian fragmentation with multiple
periods of sleep and wakefulness or severe sleeplessness.)
Illusions and hallucinations can be of any sensory modality. Misperceptions are “simple” if they are uncomplicated, such as a sound,
noise, color, spot, or flashes and ‘‘complex’’ if they are multidimensional, such as voices, music, people, animals, or scenes. Rateifreported
by patient or caregiver, or inferred by observation.
Perceptual disturbances and hallucinations
Mild perceptual disturbances (e.g., feelings of derealization or depersonalization; or patient may not be able to discriminate dreams
Delusions can be of any type, but are most often persecutory. Rate if reported by patient, family or caregiver. Rate as delusional if ideas
are unlikely to be true yet are believed by the patient who cannot be dissuaded by logic. Delusional ideas cannot be explained otherwise
by the patient’s usual cultural or religious background.
Mildly suspicious, hypervigilant, or preoccupied
Unusual or overvalued ideation that does not reach delusional proportions or could be plausible
Rate the patient’s affect as the outward presentation of emotions and not as a description of what the patient feels.
Lability of affect
Affect somewhat altered or incongruent to situation; changes over the course of hours; emotions are mostly under self-control
Affect is often inappropriate to the situation and intermittently changes over the course of minutes; emotions are not consistently
under self-control, though they respond to redirection by others
Severe and consistent disinhibition of emotions; affect changes rapidly, is inappropriate to context, and does not respond to redi-
rection by others
Rate abnormalities of spoken, written or sign languagethat cannot beotherwiseattributedtodialectorstuttering.Assessfluency,grammar,
comprehension, semantic content and naming. Test comprehension and naming nonverbally if necessary by having patient follow com-
mands or point.
Mild impairment including word-finding difficulty or problems with naming or fluency
Moderate impairment including comprehension difficulties or deficits in meaningful communication (semantic content)
Severe impairment including nonsensical semantic content, word salad, muteness, or severely reduced comprehension
240 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
Rate abnormalities of thinking processes based on verbal or written output. If a patient does not speak or write, do not rate this item.
Thought process abnormalities
Normal thought processes
Tangential or circumstantial
Associations loosely connected occasionally, but largely comprehensible
Associations loosely connected most of the time
Rate by observation, including from other sources of observation such as by visitors, family and clinical staff. Do not include dyskinesia,
tics, or chorea.
No restlessness or agitation
Mild restlessness of gross motor movements or mild fidgetiness
Moderate motor agitation including dramatic movements of the extremities, pacing, fidgeting, removing intravenous lines, etc.
Severe motor agitation, such as combativeness or a need for restraints or seclusion
Rate movements by direct observation or from other sources of observation such as family, visitors,orclinicalstaff.Donotratecomponents
of retardation that are caused by parkinsonian symptoms. Do not rate drowsiness or sleep.
No slowness of voluntary movements
Mildly reduced frequency, spontaneity or speed of motor movements, to the degree that may interfere somewhat with the
Moderately reduced frequency, spontaneity or speed of motor movements to the degree that it interferes with participation in
activities or self-care
Severe motor retardation with few spontaneous movements.
Patients who cannot speak can be given a visual or auditory presentation of multiple choice answers. Allow patient to be wrong by up
to 7 days instead of 2 days for patients hospitalized more than 3 weeks. Disorientation to person means not recognizing familiar persons
and may be intact even if the person has naming difficulty but recognizes the person. Disorientation to person is most severe when one
doesn’t know one’s own identity and is rare. Disorientation to person usually occurs after disorientation to time and/or place.
Oriented to person, place and time
Disoriented to time (e.g., by more than 2 days or wrong month or wrong year) or to place (e.g., name of building, city, state), but
Disoriented to time and place
Disoriented to person
Patients with sensory deficits or who are intubated or whose hand movements are constrained should be testedusinganalternatemodality
besides writing. Attention can be assessed during the interview (e.g., verbal perseverations, distractibility, and difficulty with set shifting)
and/or through use of specific tests, e.g., digit span.
Alert and attentive
Mildly distractible or mild difficulty sustaining attention, but able to refocus with cueing. On formal testing makes only minor
errors and is not significantly slow in responses
Moderate inattention with difficulty focusing and sustaining attention. On formal testing, makesnumerouserrorsandeitherrequires
prodding to focus or finish the task
Severe difficulty focusing and/or sustaining attention, with many incorrect or incomplete responses or inability to follow instruc-
tions. Distractible by other noises or events in the environment
Defined as recall of information (e.g., 3 items presented either verbally or visually) after a delay of about 2 to 3 minutes. When formally
tested, information must be registered adequately before recall is tested. The number of trials to register as well as effect of cueing can be
noted on scoresheet. Patient should not be allowed to rehearse during the delay period and should be distracted during that time. Patient
may speak or nonverbally communicate to the examiner the identity of the correct items. Short-term deficits noticed during the course of
the interview can be used also.
Short-term memory intact
Recalls 2/3 items; may be able to recall third item after category cueing
Recalls 1/3 items; may be able to recall other items after category cueing
Recalls 0/3 items
J Neuropsychiatry Clin Neurosci 13:2, Spring 2001241
TRZEPACZ et al.
Can be assessed formally or through interviewing for recall of past personal (e.g., past medical history or information or experiences that
can be corroborated from another source) or general information that is culturally relevant. When formally tested, use a verbal and/or
visual modality for 3 items that are adequately registered and recalled after at least 5 minutes. The patient should not be allowed to
rehearse during the delay period during formal testing. Make allowances for patients with less than 8 years of education or who are
mentally retarded regarding general information questions. Rating of the severity of deficits may involve a judgment about all the ways
long-term memory is assessed, including recent and/or remote long-term memory ability informally tested during the interview as well
as any formal testing of recent long-term memory using 3 items.
No significant long-term memory deficits
Recalls 2/3 items and/or has minor difficulty recalling details of other long-term information
Recalls 1/3 items and/or has moderate difficulty recalling other long-term information
Recalls 0/3 items and/or has severe difficulty recalling other long-term information
Assess informally and formally. Consider patient’s difficulty navigating one’s way around living areas or environment (e.g., getting lost).
Test formally by drawing or copying a design, by arranging puzzle pieces, or by drawing a map and identifying major cities, etc. Take
into account any visual impairments that may affect performance.
Mild impairment such that overall design and most details or pieces are correct; and/or little difficulty navigating in his/her
Moderate impairment with distorted appreciation of overall design and/or several errors of details or pieces; and/or needing
repeated redirection to keep from getting lost in a newer environment despite, trouble locating familiar objects in immediate
Severe impairment on formal testing; and/or repeated wandering or getting lost in environment
? Trzepacz 1998
DRS-R-98 OPTIONAL DIAGNOSTIC ITEMS
These three items can be used to assist in the differentiation of delirium from other disorders for diagnostic and research purposes. They
are added to the severity score for the total scale score, but are NOT included in the severity score.
Rate the acuteness of onset of the initial symptoms of the disorder or episode being currently assessed, not their total duration.Distinguish
the onset of symptoms attributable to delirium when it occurs concurrently with a different preexisting psychiatric disorder. For example,
if a patient with major depression is rated during a delirium episode due to an overdose, then rate the onset of the delirium symptoms.
Temporal onset of symptoms
No significant change from usual or longstanding baseline behavior
Gradual onset of symptoms, occurring over a period of several weeks to a month
Acute change in behavior or personality occurring over days to a week
Abrupt change in behavior occurring over a period of several hours to a day
Rate the waxing and waning of an individual or cluster of symptom(s) over the time frame being rated. Usually applies to cognition,
affect, intensity of hallucinations, thought disorder, language disturbance. Take into consideration that perceptual disturbances usually
occur intermittently, but might cluster in period of greater intensity when other symptoms fluctuate in severity.
Fluctuation of symptom severity
No symptom fluctuation
Symptom intensity fluctuates in severity over hours
Symptom intensity fluctuates in severity over minutes
Rate the degree to which a physiological, medical or pharmacological problem can be specifically attributed to have caused the symptoms
being assessed. Many patients have such problems but they may or may not have causal relationship to the symptoms being rated.
None present or active
Presence of any physical disorder that might affect mental state
Drug, infection, metabolic disorder, CNS lesion or other medical problem that specifically can be implicated in causing the altered
behavior or mental state
? Trzepacz 1998
242 J Neuropsychiatry Clin Neurosci 13:2, Spring 2001
DELIRIUM RATING SCALE-REVISED-98
Name of patient: Date: / /Time:
Name of Rater:
SEVERITY SCORE:TOTAL SCORE:
Severity Item Item Score
Sleep-wake cycle123 Naps Nocturnal disturbance only
Sensory type of illusion or hallucination:
Format of illusion or hallucination:
Type of delusion:
Lability of affect0123 Type: angry
Language0123 Check here if intubated, mute, etc.
Thought process0123 Check here if intubated, mute, etc.
Motor agitation0123 Check here if restrained
Type of restraints:
Check here if restrained
Type of restraints:
3 Record # of trials for registration of items:
Check here if category cueing helped
Long-term memory0123 Check here if category cueing helped
Visuospatial ability0123 Check here if unable to use hands
Diagnostic ItemItem Score Optional Information
Temporal onset of symptoms0123Check here if symptoms appeared on a background of other
Check here if symptoms only appear during the nightFluctuation of symptom