Lay abstracts

Lay abstract: When embarking on the difficult task of estimating the proportion of the population with autism spectrum disorder (ASD), it is not typically possible to assess every individual in the target population with costly “gold standard” diagnostic procedures. Some studies first screen the total population using an inexpensive assessment tool (e.g. with a questionnaire), and then concentrate full diagnostic evaluations on individuals who have been identified as being more likely to have ASD during the preliminary screening. Statistical procedures are used to generalize back to the entire population. Although this “two-phase” design can potentially allow for a more efficient deployment of resources, this approach can also introduce methodological complications, leading to estimates that may be inaccurate or imprecise. We examined these potential pitfalls in the context of a recent high-profile finding by Kim et al. (2011, Prevalence of autism spectrum disorders in a total population sample: American Journal of Psychiatry 168: 904–912), who estimated that ASD affects 2.64% of children in a South Korean community. We reconstructed the study’s methodology and used computer simulations to reassess whether their point estimate (2.64%) and reported precision (a plausible range of 1.91%–3.37%) were reasonable, given what was known about their screening instrument and their participants. We found the original estimate to be highly dependent upon certain initial assumptions (for example, assumptions about whether families who chose to participate in the study differed meaningfully from those who chose not to). Further, although the authors reported a plausible range of 1.91%–3.37%, we suggest that this range should probably be twice as wide. Future studies should give serious consideration to the additional sources of uncertainty introduced by two-phase designs, which may easily outstrip any expected gains in efficiency. Title: Factor structure and psychometric properties of the revised Home Situations Questionnaire for autism spectrum disorder: The Home Situations Questionnaire-Autism Spectrum Disorder