The Autism Symptom Dimensions Questionnaire: Development and psychometric evaluation of a new, open-source measure of autism symptomatology

Aim: To describe the development and initial psychometric evaluation of a new, freely available measure, the Autism Symptom Dimensions Questionnaire (ASDQ). Method: After development and revision of an initial 33-item version, informants completed a revised 39-item version of the ASDQ on 1467 children and adolescents (aged 2-17 years), including 104 with autism spectrum disorder (ASD). Results: The initial 33-item version of the ASDQ had good reliability and construct validity. However, only four specific symptom factors were identified, potentially due to an insufficient number of items. Factor analyses of the expanded instrument identified a general ASD factor and nine specific symptom factors with good measurement invariance across demographic groups. Scales showed good-to-excellent overall and conditional reliability. Exploratory analyses of predictive validity for ASD versus neurotypical and other developmental disability diagnoses indicated good accuracy for population and at-risk contexts. Interpretation: The ASDQ is a free and psychometrically sound informant report instrument with good reliability of measurement across a continuous range of scores and preliminary evidence of predictive validity. The measure may be a useful alternative to existing autism symptom measures but further studies with comparison of clinical diagnoses using criterion-standard instruments are needed