Clinician Diagnostic Certainty and the Role of the Autism Diagnostic Observation Schedule in Autism Spectrum Disorder Diagnosis in Young Children.

Importance: Autism spectrum disorder (ASD) affects 1 in 44 children. The Autism Diagnostic Observation Schedule (ADOS) is a semi-structured observation developed for use in research but is considered a component of gold standard clinical diagnosis. The ADOS adds time and cost to diagnostic assessments. Objective: To evaluate consistency between clinical diagnosis (index ASD diagnosis) and diagnosis incorporating the ADOS (reference standard ASD diagnosis) and to examine clinician and child factors that predict consistency between index diagnoses and reference standard diagnoses. Design, Setting, and Participants: This prospective diagnostic study was conducted between May 2019 and February 2020. Developmental-behavioral pediatricians (DBPs) made a diagnosis based on clinical assessment (index ASD diagnosis). The ADOS was then administered, after which the DBP made a second diagnosis (reference standard ASD diagnosis). DBPs self-reported diagnostic certainty at the time of the index diagnoses and reference standard diagnoses. The study took place at 8 sites (7 US and 1 European) that provided subspecialty assessments for children with concerns for ASD. Participants included children aged 18 months to 5 years, 11 months, without a prior ASD diagnosis, consecutively referred for possible ASD. Among 648 eligible children, 23 refused, 376 enrolled, and 349 completed the study. All 40 eligible DBPs participated. Exposures: ADOS administered to all child participants. Main Outcomes and Measures: Index diagnoses and reference standard diagnoses of ASD (yes/no). Results: Among the 349 children (279 [79.7%] male; mean [SD] age, 39.9 [13.4] months), index diagnoses and reference standard diagnoses were consistent for 314 (90%) (ASD = 250; not ASD = 64) and changed for 35. Clinician diagnostic certainty was the most sensitive and specific predictor of diagnostic consistency (area under curve = 0.860; P < .001). In a multilevel logistic regression, no child or clinician factors improved prediction of diagnostic consistency based solely on clinician diagnostic certainty at time of index diagnosis. Conclusions and Relevance: In this prospective diagnostic study, clinical diagnoses of ASD by DBPs with vs without the ADOS were consistent in 90.0% of cases. Clinician diagnostic certainty predicted consistency of index diagnoses and reference standard diagnoses. This study suggests that the ADOS is generally not required for diagnosis of ASD in young children by DBPs and that DBPs can identify children for whom the ADOS may be needed.