Exploring the boundaries of pervasive developmental disorder not otherwisespecified: Analyses of data from the DSM-IV autistic disorder field trial

This study aimed to explore the boundaries between PDD and related disorder s and to develop classificatory algorithms for what is currently called Per vasive Developmental Disorder Not Otherwise Specified (PDDNOS). Data collec ted by means of a standard coding system for the DSM-IV field trial for aut istic disorder were used. Information on diagnostic criteria for autistic d isorder as listed in ICD-10 and DSM-IV was compared between subjects functi oning at least in the mildly retarded range and clinically classified as au tistic disorder (n = 205), PDDNOS (n = 80) and other non-PDD disorders (n = 174). Only a limited number of items from the ICD-IO and DSM-TV systems fa r autistic disorder significantly discriminated the PDDNOS group from other disorders. A scoring rule based on a short set of 7 ICD-10/DSM-IV criteria with a cutoff of 3 items and I social interaction item set as mandatory ha d the best balance between high sensitivity and high specificity in discrim inating PDDNOS from non-PDD disorders. These rules yielded a somewhat bette r prediction than most effective rules based on the full set of 12 criteria for autistic disorder with a cutoff of 4 items and I social item as mandat ory. Generally accepted and well-validated criteria to identify individuals with PDDNOS should facilitate both research and clinical services.