Background: Autism spectrum disorder (ASD) is a lifelong neurodevelopmental condition affecting 1.1% of adults. The increasing incidence of ASD has led to pressurised diagnostic services. Objective: We aimed to determine the number needed to harm (NNH) of criteria-informed triage assessment in an adult autism diagnostic service in the UK. Methods: The study was conducted at a specialist adult Autism Service in West Yorkshire, UK, from November 2021 to August 2022. All eligible referrals were accepted, with criteria requiring service users to be over 18 years old and without an intellectual disability. The evaluation consisted of 60 cases. Results: None of the evaluation cases resulted in a clinical diagnosis of ASD, yielding an infinite number needed to harm (NNH), demonstrating that every case benefited from the triage process without significant risk of harm. Conclusions: Triage enables services to gather comprehensive information about individual presentations and clinical needs, facilitating informed decision-making and better service utilisation. The evaluation demonstrates the safety and effectiveness of the triage process, with directions for further research discussed.
Keywords: adult autism; adult autism diagnosis; autism; autism diagnosis.