Clinical correlates of diagnostic certainty in children with autism

Abstract

Background Clinicians diagnosing autism rely on diagnostic instruments and criteria in combination with an implicit knowledge of the specific signs and presentations associated with the condition, based on clinical expertise. This implicit knowledge influences how diagnostic criteria are interpreted but cannot be directly observed. Instead, insight into clinicians’ understanding of autism can be gained by investigating their diagnostic certainty. Modest correlations between the certainty of an autism diagnosis and symptom load have been previously reported. Here, we investigated the associations of diagnostic certainty with specific items of the ADOS as well as other clinical features including head circumference. Methods Phenotypic data from the Simons Simplex Collection was used to investigate clinical correlates of diagnostic certainty in individuals with autism. Participants were stratified by the ADOS module used to evaluate them. We investigated how diagnostic certainty was associated with total ADOS scores, age, and ADOS module. We calculated the odds-ratios of being diagnosed with the highest possible certainty given the presence or absence of different signs during the ADOS evaluation. Associations between diagnostic certainty and other cognitive and clinical variables were also assessed. Results Some ADOS items showed a larger association with diagnostic certainty than others. Head circumference was significantly higher for individuals with the highest certainty rating across all three ADOS modules. In turn, head circumference was positively correlated with some of those ADOS items that were associated with diagnostic certainty, particularly in ADOS module 2. Limitations: The investigated cohort was heterogeneous, possibly impeding the identification of associations that only exist in a subgroup of the population. The scoring of diagnostic certainty may vary between clinicians. Conclusion Some ADOS items may better capture the signs that are most associated with clinicians’ implicit knowledge of autism. If replicated in future studies, new diagnostic instruments with differentiated weighting of signs may be needed to better reflect this, possibly resulting in better specificity in standardized assessments.