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: Sol FORTEA Sevilla03/2012, Supervisor: PhD MO Escandell Bermúdez and PhD JJ Castro Pérez
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ABSTRACT: This systematic literature review explored the state of the art concerning the theoretical and empirical knowledge of the twice-exceptionality of Intellectual Giftedness and Autism Spectrum Disorders (IG + ASD)3, in relation to diagnostic and assessment issues. After searching and examining publications in peer-reviewed journals and dissertations, we encountered a variety of methodologies being used. The results showed the absence, until now, of theoretical conceptualisations of the phenomenon IG + ASD. Nevertheless, this contribution revealed some converging tendencies concerning both personal characteristics and diagnostic and assessment issues, between publications with and without Systematic Identification Measures (SIM). Some findings, like the ‘superior non-verbal abilities’, are discussed in relation to (controversial) image formation of IG and IG + ASD. Altogether, the results indicated the need for an in-depth exploration and conceptualisation of the phenomenon IG + ASD. Meanwhile, future research should also address the practical psychological-educational need for both classification-based and needs-based assessment procedures, regarding students with (suspicion of) IG + ASD.Educational Research Review 10/2010; 6(1):67-88. DOI:10.1016/j.edurev.2010.10.001 · 2.33 Impact Factor