Domains of the Childhood Autism Rating Scale: relevance for diagnosis and treatment.

The Childhood Autism Rating Scale (CARS) was factor analyzed. Three factors emerged: Social Impairment (SI), Negative Emotionality (NE), and Distorted Sensory Response (DSR). Unit-weight factor scales showed moderate-to-good internal consistency. Cross-sectional analyses demonstrated that autistic (AUT) subjects were distinguished from subjects with pervasive developmental disorders (PDD) and nonpervasive developmental disorders (NPDD) by higher scores on SI. An SI cutoff score of 26 classified individuals as autistic vs. nonautistic with 78% accuracy. Longitudinal analyses showed that DSR was stable over 6 months of treatment, with little indication of symptom reduction. SI decreased over time across the diagnostic groups, but still showed significant continuity over the period. NE was most malleable and apparently sensitive to the effects of treatment.