Factor analysis of the autism spectrum screening questionnaire in a population-based child sample.

Purpose: The aim of this study was to investigate several possible factor structures of the Autism Spectrum Screening Questionnaire (ASSQ).
Materials and Methods: We used the 27-item screening tool for school-aged children in a general population of 8-year-old children ( n  = 3,538) and compared the occurring solutions to previously published factor models.
Results: A one-factor solution and a four-factor solution were identified in Exploratory Factor Analysis (EFA) and confirmed with Confirmatory Factor Analysis (CFA), while two-, three-, five- and six-factor solutions were rejected. In CFA, our four-factor solution showed the best goodness-of-fit indexes when compared with factor models previously presented by Posserud et al. and Ehlers et al.
Conclusions: The results indicate a strong underlying connection between all ASSQ items which is elicited by the one-factor solution. Although as a screening tool, ASSQ is functioning with the unifactorial solution, the four factors can help to identify certain clusters of autism spectrum traits.