Can screening measures for autism in adults predict diagnosis?

Abstract 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. Aims: To test the predictive validity of three screening measures: the Autism Spectrum Quotient (AQ) and Empathy Quotient (EQ) (both self-report), and the Relatives Questionnaire (RQ) (retrospective parent/informant-report). Methods: N=460 adults attending a specialist diagnostic service between January 2011 and December 2014 in England were 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. Conclusion: 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. Our finding that the 3 screeners combined have a PPV of 98% means that services can be confident that those who screen positive on all three measures are in fact likely to be affected by the condition. With services under increasing pressure, referrals can be triaged on the basis of screening profiles, creating the opportunity for services to develop a pathway that includes an accelerated assessment for those screening positive on all measures. This would save resources for the more complex referrals or those with an atypical screening presentation.National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research & Care (CLAHRC) East of England and Cambridgeshire & Peterborough NHS Foundation Trust, Autism Research Trust, the MRC, the Templeton World Charitable Trust, and the NIHR Cambridge Biomedical Research Centre, Innovative Medicines Initiative 2 Joint Undertaking (JU) under grant agreement No 777394. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and EFPIA and AUTISM SPEAKS, AUTISTICA, SFAR