Prevalence of autism spectrum disorder in a large pediatric primary care network
Authors: Wallis Kate E , Adebajo Toore , Bennett Amanda E , Drye Madison , Gerdes Marsha , Miller Judith S , Guthrie Whitney 
Published: January 2023

In this retrospective cohort study using data from an integrated primary care and subspecialty network, we examined medical records of children seen in primary care at eligible autism spectrum disorder (ASD) screening ages and followed through at least 4 years of age. We examined the prevalence of ASD; age of first documented ASD diagnosis; and whether the prevalence and age of documented diagnosis varied by race, ethnicity, socio-economic status (SES) and site of care (urban versus suburban/rural). The prevalence of ASD across the cohort was 3.2%, with a median age of diagnosis of 3.93 years. ASD prevalence was unexpectedly higher among Asian children, non-Hispanic Black children, children with higher Social Vulnerability Index scores (a neighborhood-level proxy of socio-economic risk), and children who received care in urban primary care sites. There were no statistically significant differences in age at which ASD diagnosis was documented across socio-demographic groups. Receiving primary care at an urban site accounted for most other socio-demographic differences in ASD prevalence rates, except among Asian children, who were found to have higher adjusted odds of ASD diagnosis compared to White children (aOR = 1.82, p < .001). Determining what clinical-, individual- or systems-level factors contribute to ASD diagnosis remains important to improve equity. Lay Abstract Historically, children from non-Hispanic Black and Hispanic backgrounds, those from lower-income families, and girls are less likely to be diagnosed with autism spectrum disorder. Under-identification among these historically and contemporaneously marginalized groups can limit their access to early, autism spectrum disorder-specific interventions, which can have long-term negative impacts. Recent data suggest that some of these trends may be narrowing, or even reversing. Using electronic health record data, we calculated autism spectrum disorder prevalence rates and age of first documented diagnosis across socio-demographic groups. Our cohort included children seen at young ages (when eligible for screening in early childhood) and again at least after 4 years of age in a large primary care network. We found that autism spectrum disorder prevalence was unexpectedly higher among Asian children, non-Hispanic Black children, children with higher Social Vulnerability Index scores (a measure of socio-economic risk at the neighborhood level), and children who received care in urban primary care sites. We did not find differences in the age at which autism spectrum disorder diagnoses were documented in children’s records across these groups. Receiving primary care at an urban site (regardless of location of specialty care) appeared to account for most other socio-demographic differences in autism spectrum disorder prevalence rates, except among Asian children, who remained more likely to be diagnosed with autism spectrum disorder after controlling for other factors. We must continue to better understand the process by which children with autism spectrum disorder from traditionally under-identified and under-served backgrounds come to be recognized, to continue to improve the equity of care.