Assessing subtypes of restricted and repetitive behaviour using the Adult Repetitive Behaviour Questionnaire-2 in autistic adults.

The final analysed sample was 275 adults; 352 initially reported a diagnosis and 309 met the AQ cut-off. The sample was not representative of autistic adults overall: it was mostly white (92.6%), had 171 women and 100 men, and required reading ability to complete the questionnaire online. Autism diagnoses were self-reported and not independently confirmed, and IQ or cognitive ability was not measured. The AQ cut-off of 26 was lower than the original cut-off of 32, and using the higher cut-off changed how some items loaded. The structure was tested with exploratory PCA only; confirmatory factor analysis was not done. Some sensory items were unstable: angles and smell did not load clearly, and arrange and carry changed depending on the AQ cut-off.

Funding came from the Economic and Social Research Council and the School of Psychology, Cardiff University. The supplied text does not state author competing interests.

Do not treat the RBQ-2A as a diagnostic test or use its two clusters to infer that autism subtypes can be treated. The study did not test treatment. The sample was self-reported, online, mostly highly educated, mostly white, and not confirmed for diagnosis or IQ.