Validity of the Systemizer Profile Questionnaire: A New Tool to Identify Cognitive, Mentalizing, Sensory, Social, and Systemizing Abilities in Adults with Autism-Spectrum-Disorders With and Without Comorbid ADHD

PURPOSE: Systemizer Profile Questionnaire (SPQ), which has not been used before, investigates difficulties in mentalisation, sensory- and/or social sensitivity and social cognition (MSSSC) in subjects with Autism-Spectrum-Disorders (ASD) with and without Attention-Deficit-Hyperactivity-Disorder (ADHD). The aim of this study was to evaluate the reliability and validity of the SPQ domains, and to assess the predictive validity of the SPQ against the Ritvo Autism Asperger Diagnostic Scale (RAADS).

METHODS: Three-hundred-fifty-four study subjects with ICD-10 verified ASD confirmed by RAADS and 354 controls matched on age group and gender were recruited and evaluated systematically with SPQ, standardized questions about demographic and clinical data. Hypothesized SPQ subscales formed from 85 items were evaluated using confirmatory factor analysis (CFA). Resulting revised sub-scales were confirmed using item response theory (IRT) and the predictive validity of the SPQ scores was evaluated using RAADS scores above 64 as the standard.

RESULTS: Twenty-two of the original 85 items were removed, resulting in an instrument with 63 items across nine psychometrically valid domains. These domains had high sensitivity (range: 0.64 to 0.84), and high specificity (range: 0.73 to 0.90). Positive predictive values (range: 0.76 to 0.89) and negative predictive values (range: 0.69 to 0.90) were also high. For the total SPQ score the sensitivity was 0.95, the specificity was 0.87, the positive predictive value was 0.88 and the negative predictive value was 0.95.

CONCLUSION: SPQ domains are valid descriptions/profiles of MSSSC given that ASD is confirmed by RAADS, though irrelevant if not, as SPQ is not a diagnostic instrument.