The structure of autism symptoms as measured by the autism diagnostic observation schedule

The current study tested several competing models of the autism phenotype using data from modules 1 and 3 of the ADOS. Participants included individuals with ASDs aged 3-18 years (N = 1,409) from the AGRE database. Confirmatory factor analyses were performed on total samples and subsamples based on age and level of functioning. Three primary models were tested, including a one-factor model, the DSM-IV model, and the anticipated DSM-V model. Results indicated all models fit similarly. Module 1 ratings yielded better indices of fit across all models and higher inter-factor correlations than Model 3. Model fits were impacted by age and level of functioning. The lack of differentiation between models suggests that the structure of ASD symptoms is complex to measure statistically.