Testing adults by questionnaire for social and communication disorders, including autism spectrum disorders, in an adult mental health service population

Objectives: Autism is difficult to identify in adults due to lack of validated self-report questionnaires. We compared the effectiveness of the autism-spectrum quotient (AQ) and the Ritvo autism–Asperger's diagnostic scale-revised (RAADS-R) questionnaires in adult mental health services in two English counties. Methods: A subsample of adults who completed the AQ and RAADS-R were invited to take part in an autism diagnostic observation schedule (ADOS Module 4) assessment with probability of selection weighted by scores on the questionnaires. Results: There were 364 men and 374 women who consented to take part. Recorded diagnoses were most commonly mood disorders (44%) and mental and behavioural disorders due to alcohol/substance misuse (19%), and 4.8% (95% CI [2.9, 7.5]) were identified with autism (ADOS Module 4 10+). One had a pre-existing diagnosis of autism; five (26%) had borderline personality disorders (all female) and three (17%) had mood disorders. The AQ and RAADS-R had fair test accuracy (area under receiver operating characteristic [ROC] curve 0.77 and 0.79, respectively). AQ sensitivity was 0.79 (95% CI [0.54, 0.94]) and specificity was 0.77 (95% CI [0.65, 0.86]); RAADS-R sensitivity was 0.75 (95% CI [0.48, 0.93]) and specificity was 0.71 (95% CI [0.60, 0.81]). Conclusions: The AQ and RAADS-R can guide decisions to refer adults in mental health services to autism diagnostic services.