Exploring the Predictive Value of Early Adaptive Functioning on ASD Diagnostic Trajectories

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by early deficits in social, communicative, and adaptive functioning. Given the rising prevalence of ASD, this study examines whether early adaptive behavior corresponds with later ASD diagnostic trajectories. Early diagnosis is critical for intervention, yet diagnostic stability in longitudinal studies varies across cases. Diagnostic instability refers to cases in which an ASD diagnosis is delayed, lost, or inconsistent across time. The Vineland Adaptive Behavior Scales (VABS), a standardized measure of adaptive functioning across multiple domains, assesses participants' strengths and weaknesses. The present study uses standardized adaptive scores at 6, 12, and 24 months to investigate if early adaptive trajectories are a potential marker of diagnostic stability from toddlerhood to school age. Participants (N=213) were recruited through the NIH-funded Infant Brain Imaging Study (IBIS), a network that tracks infants with a high likelihood for ASD due to having an older sibling with ASD. The relationship between diagnostic trajectory and adaptive scores over time was analyzed using latent class mixed modeling and a growth curve analysis. The latent class mixed modeling analysis showed a significant but modest relationship between adaptive latent class and diagnostic group. In the growth curve analysis, there were some significant differences in slope across domains between the always negative group (ASD-) to the always positive (ASD+) and positive to negative group, and an intermediate adaptive profile corresponding with the inconsistent cases was identified. These findings encourage future research to explore the predictive value of early adaptive functioning on an ASD diagnosis.