Proportion of Physicians Who Treat Patients With Greater Social and Clinical Risk and Physician Inclusion in Medicare Advantage Networks.

Importance: Medicare Advantage (MA) plans are expanding rapidly, now serving 50% of all Medicare enrollees. Little is known about how inclusion rates of physicians in MA plan networks vary by the social and clinical risks of their patients. Objective: To examine the association of physicians caring for patients with higher levels of social and clinical risk in traditional Medicare (TM) with the likelihood of inclusion in MA plan networks. Design, Setting, and Participants: This cross-sectional study evaluated the number of patients of physicians participating in TM Part B in 2019. The data analysis was conducted between June 2022 and March 2023. Exposures: Quintiles of the proportion of patients who were dually eligible for Medicare and Medicaid and average beneficiary hierarchical condition category (HCC) score (a measure of a patient's chronic disease burden that is used in risk adjustment and MA plan payment, where higher scores indicate higher risk) in the Part B TM program. Main Outcomes and Measures: The main outcomes were the proportion of MA plans and enrollees for which physicians were in network. Results: The analysis sample included 259 932 physicians billing Medicare Part B in 2019. After adjusting for physician, patient, and county characteristics, physicians with the highest quintile of patients with dual eligibility were associated with a lower likelihood of being included in MA plans and being in network with MA enrollees than the lowest quintile physicians (MA inclusion rate, -3.0% [95% CI, -3.2% to -2.8%]; P < .001; in-network enrollee proportion, -6.5% [95% CI, -7.0% to -6.0%]; P < .001). Similarly, physicians with the highest quintile HCC score were associated with a lower likelihood of being included in MA plans and being in network with MA enrollees than the lowest quintile physicians (MA inclusion rate, -7.5% [95% CI, -7.9% to -7.2%]; P < .001; in-network enrollee proportion, -18.7% [95% CI, -19.5% to -18.1%]; P < .001). Physicians in medical specialties in the highest clinical risk group (highest quintile HCC score) were associated with a significantly lower likelihood of being in network with MA enrollees than those in the lowest clinical risk group (in-network enrollee proportion, -20.4% [95% CI, -21.1% to -19.8%]; P < .001). Conclusions and Relevance: This cross-sectional study of physicians participating in TM Part B in 2019 found that physicians with higher numbers of patients with social and medical risks in TM were significantly less likely to be associated with MA plans.