Development of a Novel Self-Report Tool to Aid in the Assessment of Autism in Adulthood: The Autism Spectrum Trait Scale

Background: Autism spectrum disorder is a neurodevelopmental condition characterized by a spectrum of neuropsychological and behavioral differences. Due to historical changes in diagnostic criteria and a rapid increase in autism rates, there are likely many undiagnosed autistic adults. The current state of formal assessment for autism poses a severe ethical crisis as these assessments are often difficult to obtain, especially in adulthood. Self-report tools are sometimes used to alleviate the burden of identifying autism. However, commonly used self-report tools to aid in the identification of autistic-like traits in adults have significant limitations that threaten their reliability and validity. The purpose of this study was to develop and assess the psychometric properties of the Autism Spectrum Trait Scale (ASTS), a novel self-report tool that may aid in the identification of autistic-like traits in adults, developed using principal axis factoring procedures. Methods: Exploratory factor analysis (n = 764) was conducted to develop the factor structure, and confirmatory factor analysis (n = 761) was performed in a nonoverlapping sample to assess the factor model. Out of the 1525 participants, 507 were autistic and 1018 were not. Of the 507 autistic adults, 177 reported having a formal diagnosis, whereas 330 were self-diagnosed. Results: The results showed a stable four-factor model with good model fit (Tucker-Lewis Index [TLI] = 0.92, Comparative Fit Index [CFI] = 0.92, Goodness-of-Fit [GFI] = 0.88, root-mean-square error of approximation [RMSEA] = 0.05), strong internal consistency (α = 0.94), and criterion validity (r = 0.90, p < 0.001). The model demonstrated metric measurement invariance (Δ CFI = −0.008, Δ RMSEA = 0.001), acceptable sensitivity and specificity (area under the curve = 0.92), and the presence of a superordinate factor (TLI = 0.91, CFI = 0.92, GFI = 0.90, RMSEA = 0.05). Conclusions: These findings provide preliminary evidence for the use of the ASTS as a component of assessment for autism in adults.