Can Screening Measures for Autism in Adults Predict Diagnosis?

Background: Clinic referrals for the diagnosis of autism spectrum conditions (hereafter autism) in adults of average or above IQ are on the rise. The increase is placing pressure on clinical services to meet demand. This may partly reflect under-diagnosis of this subgroup of autism for historical reasons. Screening measures at the point of referral may aid adult services to identify those individuals who are highly likely to receive a diagnosis, enabling more efficient diagnostic procedures.

Objectives: We tested three screening measures: the Autism Spectrum Quotient (AQ) and Empathy Quotient (EQ) (both self-report), and the Relatives Questionnaire (RQ) (retrospective, parent/informant-report version of the Childhood Autism Spectrum Test) to establish which measure or combination of measures best predicted a clinical diagnosis of autism in adults.

Methods: We conducted a retrospective case review of 460 adults attending a specialist diagnostic service between January 2011 and December 2014 in England. They had been screened using the AQ, EQ, and RQ. The criterion for a diagnosis of autism was a score of >10 on the Adult Asperger Assessment (AAA) in combination with expert clinical judgement.

Results: 88% (N= 405) of the adults assessed met the criterion for a diagnosis of autism, with those who were diagnosed scoring, as predicted, significantly higher on the AQ and RQ and lower on the EQ. 9.8% (N=45) reached the cut-off score on only one measure, and 35% (N=161) reached the cut-off score on 2 measures. 51.3% (N=236) met the cut-off score on all 3 measures. Meeting the cut-off on all three measures indicated a 98% likelihood of a clinical diagnosis of autism in assessed individuals.

Conclusions: The findings from this study confirm that the combination of all 3 screening measures strongly predicts diagnosis, compared with using one or two measures alone. The results have clear implications for future research into the development and performance of short-forms of the 3 measures and the examination of the 3-measure screening protocol to inform more efficient diagnostic pathways. With a combined PPV of 98% services can be confident that those who do screen positive on all three measures are in fact likely to be affected by the condition. Screening profiles of referrals can be triaged for progressing to an accelerated assessment for those screening positive on all measures, saving resources for the more complex referrals, or those with an atypical screening presentation.