Deconstructing the PDD clinical phenotype: Internal validity of the DSM-IV

Background: Empirical studies of the structure of autism symptoms have challenged the three-domain model of impairment currently characterizing pervasive developmental disorders (PDD). The objective of this study was to assess the internal validity of the DSM as a conceptual model for describing PDD, while paying particular attention to certain subject characteristics. Methods: Parents and teachers completed a DSM-IVreferenced rating scale for 3- to 12-year-old clinic referrals with a PDD (n = 730). Ratings were submitted to confirmatory factor analysis and different models were assessed for fit. Results: Measures of fit indicated that the three-factor solution based on the DSM was superior to other models. Most indices of fit were acceptable, but showed room for improvement. Fit indices varied according to the rater (parent or teacher), child's age (preschool versus school aged), PDD subtype (autism, Asperger's, pervasive developmental disorder not otherwise specified (PDDNOS)), and IQ. Conclusions: More research needs to be done before discarding current classification systems. Subject characteristics, modality of assessment, and procedural variations in statistical analyses impact conclusions about the structure of PDD symptoms.