Expediting clinician assessment in the diagnosis of autism spectrum disorder

AIM: To investigate a novel observational rating protocol designed to expedite clinical diagnosis of autism spectrum disorder (ASD). METHOD: Two hundred and forty patients referred to a tertiary autism center (median age 8y 9mo, range 2y 6mo–34y 8mo; 188 males, 52 females) were rated using an adaptation of the Childhood Autism Rating Scale, Second Edition (CARS‐2) based exclusively on patient observation (CARS‐2(obs)). Scores were compared to expert diagnosis of ASD, parent‐reported Social Responsiveness Scale, Second Edition (SRS‐2) and, in a selected subset of patients, the Autism Diagnostic Observation Schedule, Second Edition (ADOS‐2). RESULTS: CARS‐2(obs) distinguished patients with a clinical diagnosis of ASD from those with non‐ASD neuropsychiatric disorders (mean score=18 vs 11.7, p<0.001). Severity ratings on the CARS‐2(obs) correlated with the ADOS‐2 (r=0.68, ρ=0.64) and SRS‐2 (r=0.31, ρ=0.32). A CARS‐2(obs) cutoff point equal to or greater than 16 demonstrated 95.8% specificity and 62.3% sensitivity in discriminating individuals with ASD from individuals without ASD in a specialty referral setting. INTERPRETATION: The CARS‐2(obs) allows the rapid acquisition of quantitative ratings of autistic severity by direct observation. Coupled with parent/teacher‐reported symptoms and developmental history, the measure may contribute to a low‐cost diagnostic paradigm in clinical and public health settings, where positive results might help reduce delays in diagnosis, and negative results could prompt further specialty assessment. WHAT THIS PAPER ADDS: The Childhood Autism Rating Scale, Second Edition based on patient observation distinguished individuals with versus without autism spectrum disorder (ASD). A score equal to or greater than 16 on this assessment showed high specificity for a diagnosis of ASD.