The prevalence of autism spectrum disorders: impact of diagnostic instrument and non-response bias
ABSTRACT A large part of the variability in rates of autism spectrum disorders (ASD) across studies is non-aetiologic, and can be explained by differences in diagnostic criteria, case-finding method, and other issues of study design.
To investigate the effects on ASD prevalence of two methodological issues; non-response bias and case ascertainment. We compared the findings of using a semi-structured parent interview versus in-depth clinical assessment, including an ASD specific interview. We further explored whether including information on non-responders affected the ASD prevalence estimate.
A total population of 7- to 9-year olds (N = 9,430) was screened for ASD with the autism spectrum screening questionnaire (ASSQ) in the Bergen Child Study (BCS). Children scoring above the 98th percentile on parent and/or teacher ASSQ were invited to participate in the second and subsequently in the third phase of the BCS where they were assessed for ASD using the Development and Well-Being Assessment (DAWBA), and the Diagnostic Interview for Social and Communication disorders (DISCO), respectively.
Clinical assessment using DISCO confirmed all DAWBA ASD cases, but also diagnosed additional cases. DISCO-generated minimum prevalence for ASD was 0.21%, whereas estimated prevalence was 0.72%, increasing to 0.87% when adjusting for non-responders. The DAWBA estimate for the same population was 0.44%.
Large variances in prevalence rates across studies can be explained by methodological differences. Both information about assessment method and non-response are crucial when interpreting prevalence rates of ASD.
- SourceAvailable from: Astri J Lundervold
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- "The concept of autism has evolved from the description of severe cases of infantile autism affecting about 0.02% (Kanner, 1943), to the modern day autism spectrum disorder (ASD) encompassing an estimated 1% of the population (Baird et al., 2006; Brugha et al., 2011; Posserud, Lundervold, Lie, & Gillberg, 2010). Needless to say, the ''1% ASD'' is not the same as ''0.02% infantile autism''. "
ABSTRACT: With a view to developing a brief screening instrument for autism symptoms in a general population of adolescents, seven items from the Asperger syndrome (and high-functioning autism) diagnostic interview were adapted for use as self-report in an online questionnaire for youths aged 16-19 years (N=10,220). The selected items target lack of social understanding (4 items) and rigid and repetitive behavior and interests (RRBI; 3 items). Factor analyses were performed, and the seven items were also validated against self-reported ASD diagnosis. Best statistical model fit was found for a bifactor model with one general factor and two domain specific factors tied to social difficulties and RRBI. Both the general and the domain specific factors were associated with self-reported ASD diagnoses. The scale (referred to as the Autism Symptom SElf-ReporT for Adolescents and Adults - ASSERT) had good screening properties with a receiver operating curve-area under the curve (ROC-AUC) of 0.87 and a diagnostic odds ratio (DOR) of 15.8. Applying a modified scoring of the scale further improved the screening properties leading to a ROC-AUC of 0.89 and a DOR of 24.9. The ASSERT holds promise as a brief self-report screen for autism symptoms in adolescents, and further studies should explore its usefulness for adults.Research in developmental disabilities 10/2013; 34(12). DOI:10.1016/j.ridd.2013.09.032 · 4.41 Impact Factor
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- "The prevalence of ASD has dramatically increased to as high as approximately 9 and 11.3 per 1,000 in the US in most recent surveys in 2006 [report, 2009] and 2008 [report, 2012], respectively, and males are more often affected than females with a ratio of 4:1 [Kogan et al., 2009; Brugha et al., 2011; Chien et al., 2011b; Kim et al., 2011]. There is a large variation in the prevalence rates between studies [Brugha et al., 2011; Kim et al., 2011] explained by varied diagnostic and methodological approaches employed as well as different levels of awareness about ASD [Posserud et al., 2010]. Due to its high prevalence, long-term impairment, high genetic component, and lack of effective prevention and treatment, ASD has been prioritized for genetic studies [Merikangas and Risch, 2003]. "
ABSTRACT: Autism spectrum disorders (ASD) are childhood-onset neurodevelopmental disorders characterized by verbal communication impairments, social reciprocity deficits, and the presence of restricted interests and stereotyped behaviors. Genetic factors contribute to the incidence of ASD evidently. However, the genetic spectrum of ASD is highly heterogeneous. Chromosomal abnormalities contribute significantly to the genetic deficits of syndromic and non-syndromic ASD. In this study, we conducted karyotyping analysis in a sample of 500 patients (447 males, 53 females) with ASD from Taiwan, the largest cohort in Asia, to the best of our knowledge. We found three patients having sex chromosome aneuploidy, including two cases of 47, XXY and one case of 47, XYY. In addition, we detected a novel reciprocal chromosomal translocation between long arms of chromosomes 4 and 14, designated t(4;14)(q31.3;q24.1), in a patient with Asperger's disorder. This translocation was inherited from his unaffected father, suggesting it might not be pathogenic or it needs further hits to become pathogenic. In line with other studies, our study revealed that subjects with sex chromosomal aneuploidy are liable to neurodevelopmental disorders, including ASD, and conventional karyotyping analysis is still a useful tool in detecting chromosomal translocation in patients with ASD, given that array-based comparative genomic hybridization technology can provide better resolution in detecting copy number variations of genomic DNA. © 2013 Wiley Periodicals, Inc.American Journal of Medical Genetics Part B Neuropsychiatric Genetics 10/2013; 162(7):734-41. DOI:10.1002/ajmg.b.32153 · 3.27 Impact Factor
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- "In addition, diagnostic substitution from mental retardation to autism has been suggested to account for as much as 25 % of the increase (King and Bearman 2009). Other possible explanations for the increases include greater ASD awareness (Posserud et al. 2010), earlier age of diagnosis, changes in diagnostic criteria (Fombonne et al. 2011) and methodological differences (Wazana et al. 2007). Despite a general recognition that broader diagnostic criteria have influenced changes in prevalence, changes in diagnostic criteria and younger age at diagnosis were felt to explain only a fraction of the dramatic rise in autism diagnoses in California (Hertz- Picciotto and Delwiche 2009). "
ABSTRACT: The prevalence of autism spectrum disorders has been steadily rising. In most parts of the world, rates as high as 1 % are reported, including in the United States. In Israel, previously reported prevalence rates have been in the 0.2 % range, and were based on parental reporting of diagnosis. In this study, records from one of the largest Israeli Health Maintenance organizations were used to calculate both incidence and prevalence of autism spectrum disorder (ASD) in Israel. Israeli prevalence of ASD was calculated at 0.48 % for 1-12 years olds and 0.65 % for 8 year old children in 2010, higher than previous Israeli reports, but still lower than prevalence estimates for the US. Incidence calculations ranged from 0.65 to 0.84 per 1,000 children for children 1-12 year olds. Reasons for these differences are suggested and discussed.Journal of Autism and Developmental Disorders 07/2012; 43(4). DOI:10.1007/s10803-012-1611-z · 3.06 Impact Factor