"What does 'often' even mean?" Revising and Validating the Comprehensive Autistic Trait Inventory in Partnership with Autistic People

Background: In this study, we revised and validated the Comprehensive Autistic Trait Inventory (CATI) – a self-report inventory of autistic traits, in collaboration with autistic people. An established strength of the CATI is its ability to capture female autistic traits. Our project aimed to extend this further, to increase the inventory's accessibility, and to minimise stigma induced by deficit-based representations of autistic experience. Methods: Together with 22 individuals from the autism and autistic communities, we created the Revised Comprehensive Autistic Trait Inventory (CATI-R). Revisions included rewording items to increase clarity or reduce stigma and expanding items to capture diverse autistic experiences. Based on the revisions, we formulated a series of guidelines for developing personality-style self-report inventories of subclinical traits concerning neurodevelopmental and psychiatric divergences. The CATI-R was then validated across a large sample (n = 1439), comprising autistic (n = 375) and non-autistic participants (n = 1046), following the protocol for the original CATI. Results: We conceptually replicated the original CATI validation. A confirmatory factor analysis supported the six-subscale structure. Pearson correlations showed positive relationships between all subscales. Moreover, comparing the CATI-R with two contemporary inventories of autistic traits, we found evidence for the CATI-R's convergent validity and its ability to classify individuals as autistic or not. A measurement invariance analysis indicated that total-scale scores can be compared across genders. However, in line with current research on gender differences in autism, a repeated measures ANOVA showed subscale-specific gender differences. Accordingly, we identified different thresholds for classifying female, male, and non-binary people. Finally, a logistic regression analysis suggested that the CATI-R predicts autism particularly well in female and non-binary people. Limitations: Our study presents only initial evidence for the validity of the CATI-R that should be enriched with further analyses and types of data, including, a larger number of non-binary participants. Conclusions: This project holds significance for both research and clinical practice as it provides a trait inventory that resonates with actual autistic experience and insights for creating inventories that are sensitive, accessible, and non-stigmatising.