RESEARCH ARTICLE Open Access Predicting diagnostic outcome in adult autism spectrum disorder using the autism diagnostic observation schedule, second edition Marios Adamou 1 , Sarah L. Jones 2,3* and Stephanie Wetherhill 4 Abstract Background: The Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) module four assessment for diagnosing autism spectrum disorder in adults has shown good sensitivity and specificity in research settings. Method: This study aimed to evaluate the predictive accuracy of the ADOS-2 module four by investigating the components of the assessment, in relation to diagnostic outcome in a clinical setting. Data from 88 service users referred to a Specialist Adult Autism Service was explored. Results: ADOS-2 scores failed to predict the diagnostic outcome (overall sensitivity = 92%, specificity = 57%). Interestingly, scores from the ‘restricted interests’ component of the ADOS-2 have the potential to predict diagnostic outcome, despite this domain not been included in the scoring algorithm. Conclusions: Based on our findings, we recommend clinicians are cautious when interpreting results of the ADOS- 2 assessment. Keywords: ASD, Adult ASD, Autism, ADOS, ADOS-2, Diagnostic assessment, Multidisciplinary Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterised by pervasive difficulties in recipro- cal social interaction, alongside the presence of strict re- petitive interests and behaviours [1]. Whilst much research in ASD focuses on the developmental period, it is recognised that ASD is a lifelong condition [2–6], which is sometimes not detected clinically until later life. This delay in recognition may be explained by the observation that the ASD phenotype presents with a range of severities, language ability and intellects [7], but also because mask- ing behaviour [8, 9] or compensation strategies may not bring out sufficient impairment [10] to lead a person to a clinical assessment. Diagnosing ASD in adulthood can be difficult for a number of reasons: First, it is resource intensive due to the amount of information which needs to be collected, ideally from a variety of sources. If input from a parent or caregiver is not accessible, it can be challenging to build an accurate account of the neurodevelopmental period, as self-insight from the patient may be unreliable [11, 12]. Second, it requires a high level of specialisation by professionals who are not always available for service. Also, presentation of symptoms can greatly overlap with other disorders, specifically, negative symptoms of schizophrenia [13, 14], as well as other psychiatric co- morbidities [15], rendering the diagnostic picture com- plex [16]. This requires trained and experienced © The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. * Correspondence: sarah.jones1@swyt.nhs.uk 2 South West Yorkshire Partnership NHS Foundation Trust, Wakefield, UK 3 Manygates Clinic, Belle Isle Health Park, Portobello Road, Wakefield WF1 5PN, UK Full list of author information is available at the end of the article Adamou et al. BMC Psychiatry (2021) 21:24 https://doi.org/10.1186/s12888-020-03028-7