Ascertainment of ASD and ID

Children with a clinical impression of probable ASD undergo evaluation by a panel of experts consisting of social workers, a psychologist, and either a trained psychiatrist, developmental behavioral pediatrician, or child neurologist. The final ASD diagnosis is determined by a board-recognized developmental behavioral pediatrician. Since 1995, diagnoses of ASD are stored in a database maintained by Meuhedet as a distinct subset of the Diagnostic Classification Register. We defined ASD using the International Classification of Diseases, Ninth Revision code 299.0, 299.1, or 299.8. Intellectual disability is diagnosed in a similar manner as ASD, except that the evaluation also includes psychometric cognitive testing (diagnostic codes are in the eAppendix in the Supplement).