Tracking Changes in Primary Care Clinicians' Medicaid Participation Using Novel Methods.

Medicaid enrollees often face barriers to care due to inconsistent clinician participation. This study investigates how primary care clinicians' engagement with Medicaid evolved from 2016 to 2019, focusing on those already serving Medicaid patients at baseline. Using longitudinal data from the Transformed Medicaid Statistical Information System Analytic Files (TAFs), we analyzed changes in the number of unique Medicaid enrollees served annually by 220,665 clinicians across 40 states. We defined major increases or decreases as changes exceeding 90% of baseline enrollee volume and examined associations with clinician, practice, and state-level characteristics. The results show that while about 60% of clinicians maintained stable enrollee volumes, nearly 20% experienced substantial increases or decreases. Higher baseline enrollee volume and affiliation with community health centers were associated with greater stability, while rural practice settings were linked to higher odds of major decreases. These findings underscore the dynamic nature of Medicaid participation and highlight the need for policies that support consistent clinician engagement. As Medicaid programs face potential funding cuts and eligibility changes, tracking participation trends and reinforcing stable provider networks will be critical to safeguarding access to care.