Study: Primary care autism diagnoses vary widely by region

A new analysis of Medicaid-enrolled children found substantial geographic variation in autism spectrum disorder (ASD) diagnoses made by primary care providers (PCPs), underscoring differences in access to specialty care and local diagnostic practices. The findings were presented at the 2026 Pediatric Academic Societies (PAS) Meeting.^1,2

ASD diagnosis is often required to access disability services and early intervention therapies. Although specialists traditionally make these diagnoses, limited availability and long wait times have led some states to expand ASD diagnostic training among PCPs. However, data describing how PCPs contribute to ASD diagnosis across regions have been limited.

Study design and population

In this study, investigators analyzed Transformed Medicaid Statistical Information System Analytic Files from January 1, 2017, to June 30, 2019. The cohort included 36,263 children aged 1 to 5 years across 933 county-level groupings in 29 states. Eligible children were continuously enrolled in Medicaid and had no prior ASD diagnosis. To reduce misclassification, an additional ASD diagnosis within 6 months of the initial PCP diagnosis was required.

Regional and state-level differences in PCP diagnoses

Overall, 29% of children in the study were diagnosed with ASD by a PCP rather than a specialist. Rates varied considerably by region, with a median of 20.0% of diagnoses made by PCPs in the Midwest compared with 36.4% in the West. Within-region variation was also notable, with interquartile ranges ranging from 23.8% in the Midwest to 27.5% in the West.

State-level differences further illustrated this variability. In the Northeast, Connecticut had one of the highest median county-level rates of PCP diagnosis at 53.1%, while New Hampshire had one of the lowest at 14.3%. Similarly, in the South, South Carolina ranked among the highest at 60.4%, whereas Georgia reported a rate of 17.9%. Within-state variation also differed widely, with relatively narrow interquartile ranges in states such as Connecticut (6.2%) and New Hampshire (9.6%) and substantially broader ranges in states including Wyoming (42.3%), Illinois (37.6%), and Colorado (35.7%).

Population density showed a modest association with diagnostic patterns. County groupings in the least densely populated quartile had a median PCP diagnosis rate of 28.6% compared with 24.2% in the most densely populated quartile.

Implications for access to autism diagnosis and care

“Autism is typically diagnosed by specialists, but various factors such as long wait times can delay this process,” said the ASD3 investigative team. “Primary care providers can offer an additional pathway to early diagnosis, which is important for improving access to needed autism services and supports. Our study looked at Medicaid-enrolled children ages 1-5 in 29 states between 2017-2019, and found that 29% were diagnosed by primary care providers rather than specialists. Rates of autism diagnosis by primary care providers varied significantly between counties, states and regions. We believe that local practice patterns and specialist availability may contribute to this geographic variation."

The findings suggest that PCP involvement in ASD diagnosis is already occurring across a wide range of settings, including areas without established diagnostic training programs or proximity to large medical centers. Investigators noted that the substantial variability observed within regions and states points to the influence of local practice patterns, resource availability, and differences in specialist access.

References

1. Autism diagnosis by primary care providers: geographic variation among Medicaid-enrolled children in 29 states. Pediatric Academic Societies. News release. April 24, 2026. Accessed April 24, 2026. https://www.eurekalert.org/news-releases/1125637

2. Gorgas CA, Folch DC, Charlesworth C, et al. Autism diagnosis by primary care providers: geographic variation among medicaid-enrolled children in 29 states. Presented at: 2026 PAS Meeting. April 24-27, 2026; Boston, MA.