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.
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ABSTRACT: To describe the prevalence of DSM-IV disorders and comorbidity in a large school-based sample of 6-17 year old children and adolescents in northeast China.PLoS ONE 10/2014; 9(10):e111223. · 3.53 Impact Factor
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ABSTRACT: This paper extensively and comprehensively reviews the literature on epidemiology of autism focusing on the prevalence rates of Autistic Disorder (AD) and Autism Spectrum Disorder (ASD), and the potential negative impact of DSM-5 ASD on future ASD prevalence studies. Between 1966 and 2013, there are 72 published prevalence studies of AD and 61 published studies of ASD. The AD has a broad range of prevalence rates and has shown a trend of increasing rates over time. But there are also some evidences showing that the increase seems to have leveled off. The current prevalence of AD is estimated in the range of 10–30 per 10,000 people (i.e., 1 in 1000 to 1 in 333). The ASD also has a wide range of prevalence rates with a median rate of 69.5 per 10,000 people (1 in 144). When the prevalence rates are subdivided into several sub-ranges (e.g., 10–20, 20–40, etc. per 10,000), it is difficult to pick a particular sub-range to represent the prevalence of ASD. The present review notes that several recent studies comparing the utility of DSM-IV/DSM-IV-TR ASD and the DSM-5 ASD have reported that about 9–54% of DSM-IV ASD cases do not qualify for the DSM-5 ASD. Suggestions of research designs for future ASD prevalence studies are offered.Research in Autism Spectrum Disorders 11/2014; 8(11):1454–1470. · 2.96 Impact Factor
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ABSTRACT: In a defined geographical area in the south of the UK, 115 children with active epilepsy (i.e., children who had seizures in the last year and/or children who are currently taking antiepileptic drugs (AEDs)) were identified via a computerized database and liaison with local pediatricians. Eighty-five (74%) of the children (5-15years of age) underwent a comprehensive psychological assessment. Twenty-one percent of the children met the DSM-IV-TR criteria for ASD, and 61% of them had another DSM-IV-TR behavioral or motor disorder. The Autism Spectrum Screening Questionnaire (ASSQ) was completed by parents (n=69) and by teachers (n=67) of children with an IQ>34. Only 9% of children on parent ratings and 15% of children on teacher ratings had no features of ASD. Parents reported significantly (p<.05) more features of ASD on the ASSQ compared with teachers. Factors significantly associated with responses on the ASSQ included respondent (parents reported more features), school placement (more features in specialized settings), and respondent by school placement interaction. Effective screening for ASD in children with epilepsy will need a consideration of the impact of informant and school placement on ratings. In conclusion, features of ASD were common in children with epilepsy regardless of cognitive ability. The ASSQ was a useful screening instrument in this population, and combining parent and teacher forms was optimal in terms of screening properties. Copyright © 2014. Published by Elsevier Inc.Epilepsy & Behavior 12/2014; 42C:86-92. · 2.06 Impact Factor