Autism screening questionnaire: diagnostic validity.

Good interview and diagnostic measures for autism and other pervasive developmental disorders (PDDs) are available but there is a lack of a good screening questionnaire. To develop and test a screening questionnaire based on items in the best available diagnostic interview--the Autism Diagnostic Interview--Revised (ADI-R). A 40-item scale, the Autism Screening Questionnaire (ASQ), was developed and tested on a sample of 160 individuals with PDD and 40 with non-PDD diagnoses. The ASQ has good discriminative validity with respect to the separation of PDD from non-PDD diagnoses at all IQ levels, with a cut-off of 15 proving most effective. The differentiation between autism and other varieties of PDD was weaker. The ASQ is an effective screening questionnaire for PDD.