Virginia Via Research Day Book 2026

Medical Student Research Clinical

ASSOCIATION BETWEEN RESTRICTIVE AND REPETITIVE BEHAVIOR SUBTYPES AND DIAGNOSTIC DELAY IN AUTISM SPECTRUM DISORDER

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Austin Bop, DO; Natalie Rydzak, OMS-III; Logan O'Donnell, OMS-III; Claire Smith, OMS-III; Nathan Bradshaw, OMS-III Corresponding author: nbradshaw@vcom.edu

VCOM-Virginia, Blacksburg, Virginia

documentation and formal diagnosis. Based on prior literature and clinical observation, we hypothesized that B2 behaviors (insistence on sameness and inflexible adherence to routines) would be associated with delayed diagnosis. Methods: A retrospective cohort study was conducted using data from the All of Us Research Program. Individuals diagnosed with ASD before age 65 were identified using standardized diagnostic codes. Participants were categorized into four groups based on concept sets corresponding to DSM-5 Criterion B behavior domains (B1–B4). The primary outcome was the interval between the earliest documented B-criterion behavior and the date of ASD diagnosis. Group differences were assessed using a one-way analysis of variance (ANOVA). Given unequal variances and highly unequal group sizes, Games–Howell post-hoc pairwise comparisons were performed following a significant omnibus test. Results: A total of 820 individuals with ASD or ASD adjacent diagnoses were included. One-way ANOVA revealed a significant difference in time to diagnosis

across the four B-criterion groups (F(3, 3869) = 29.29, p < .001). Post-hoc analyses demonstrated that individuals presenting with B1 behaviors exhibited significantly longer diagnostic delays compared with those presenting with B2, B3, or B4 behaviors. No significant difference in diagnostic timing was observed between the B2 and B4 groups. Although the B3 group had a small sample size (n = 7), it was associated with significantly earlier diagnosis compared with all other groups. Conclusion: Specific DSM-5 restricted and repetitive behavior profiles are associated with meaningful differences in the timing of ASD diagnosis. The finding that B1 behaviors are linked to the longest diagnostic delays highlights the need for improved recognition of these presentations during early evaluation. Enhanced awareness of behavior-specific diagnostic patterns may help reduce delays and promote earlier access to intervention services.

Context: Autism spectrum disorder (ASD) is a neurodevelopmental condition that can be reliably diagnosed by 18–24 months of age; however, the timing of diagnosis varies widely despite increasing prevalence and improvements in screening practices. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) defines core ASD features under Criteria A (social communication deficits) and Criteria B (restricted, repetitive behaviors). Early diagnosis—particularly before 2.5 years of age—is associated with improved social communication, cognitive and verbal outcomes, earlier access to intervention, and reduced long-term support needs. Although early behavioral markers often precede diagnosis, variability in how restricted and repetitive behaviors are recognized may contribute to delays in referral and assessment. Objective: This study aimed to examine whether specific DSM-5 Criterion B restricted and repetitive behavior subtypes are associated with differences in the timing of ASD diagnosis. We further sought to identify which B-criterion behavior is associated with the longest interval between initial symptom

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