Primary Care Physician Network Overlap Between Medicaid and the Patient Protection and Affordable Care Act Marketplace

Abstract

This cross-sectional study quantifies Medicaid and the Patient Protection and Affordable Care Act (ACA) Marketplace overlap among primary care physicians.

Disruption of Medicaid coverage is pervasive in the US. In 2018, 23% of adult beneficiaries were disenrolled.¹ Medicaid loss is particularly salient given the end of the COVID-19 public health emergency, during which states could not involuntarily disenroll beneficiaries. States resumed Medicaid eligibility recertification in April 2023,² resulting in over 12 million disenrollments.³ Many people losing Medicaid are likely eligible for subsidized plans through the Patient Protection and Affordable Care Act Marketplace. Whether disenrolled patients have care continuity during this transition depends, in part, on the degree of overlap among clinicians accepting Medicaid and Marketplace plans. This cross-sectional study quantified Medicaid-Marketplace overlap among primary care physicians (PCPs).

Methods

Using 2020 Ideon physician directory data and rating area information from the Centers for Medicare & Medicaid Services, we identified PCPs participating in Medicaid and Marketplace plans offered in 15 states (1087 counties) with statewide Medicaid networks. PCPs were non–hospital-based physicians with a primary specialty in internal, family, or general medicine. The Vanderbilt University institutional review board did not consider this human participant research. We followed the STROBE reporting guideline.

We quantified overlap among Medicaid-participating PCPs for the average Marketplace network. For each pair of Medicaid and Marketplace networks offered in a county, the denominator was the number of PCPs located in the county’s Marketplace rating area that participated in the Medicaid program. The numerator was the number of PCPs who also participated in the Marketplace network. We calculated the overlap separately for every Medicaid-Marketplace pair and across Marketplace networks to obtain a mean overlap value. We calculated a county-level overlap measure describing how many Medicaid-participating PCPs participated in any Marketplace network. The denominator was the number of Medicaid-participating PCPs, and the numerator was the number of PCPs participating in any available Marketplace network. For both measures, we obtained population-weighted state means across all counties. All analyses were conducted in R, version 4.1.1 from June 2023 to December 2023.

Results

Mean PCP Medicaid Marketplace overlap was 28.8% (95% CI, 27.4%-30.3%) (Figure 1). Overlap varied from 59.6% (95% CI, 57.9%-61.3%) in Iowa to 8.5% (95% CI, 6.1%-11.0%) in South Carolina and was more variable by county, from 78.0% (95% CI, 75.6%-80.3%) to 3.4% (95% CI, 1.9%-4.9%). Overlap was higher (56.7%; 95% CI, 53.4%-60.0%) when measuring how many Medicaid-participating PCPs participated in any Marketplace network (Figure 2). Overlap varied from 81.0% (95% CI, 78.3%-83.8%) in Iowa to 15.2% (95% CI, 10.8%-19.7%) in South Carolina. County-level overlap was more variable, from 96.1% (95% CI, 93.8%-98.4%) to 6.1% (95% CI, –2.1% to 14.2%).

Figure 1. County and Overall Mean Network Overlap by State for Average Network Overlap.

Maximum and minimum indicate the highest and lowest overlap among counties, respectively. Error bars represent 95% CIs. In the 3 states where the values are equal for each overlap measure (Delaware, New Hampshire, and Rhode Island), there is only 1 Medicaid network and 1 Marketplace rating area in the state, meaning all networks are offered statewide.

Figure 2. County and Overall Mean Network Overlap by State for Any Network Overlap.

Maximum and minimum indicate the highest and lowest overlap among counties, respectively. Error bars represent 95% CIs. In the 3 states where the values are equal for each overlap measure (Delaware, New Hampshire, and Rhode Island), there is only 1 Medicaid network and 1 Marketplace rating area in the state, meaning all networks are offered statewide.

Discussion

In 2020, 28.8% of Medicaid-participating PCPs appeared in an average Marketplace network, while 56.7% participated in any Marketplace network. Overlap varied considerably by state and county.

This analysis was limited by its restriction to the 15 states with statewide Medicaid networks, which may not be generalizable to other states if statewide networks include a lower proportion of clinicians in a county than more localized networks. The in-network status of PCPs may not adequately measure access. Research indicates “phantom” clinicians, who are in network for Medicaid patients but see few.⁴ Network data are obtained from insurers and may contain inaccuracies.⁵

Those disenrolled from Medicaid may struggle to find a Marketplace network that includes their PCP since over 40% of Medicaid-participating PCPs do not participate in local Marketplace networks. However, clinician network overlap is only important if those disenrolled from Medicaid enroll in Marketplace plans. Research shows that only 3% of those disenrolled from Medicaid enroll in a Marketplace plan within 6 months.⁶ While addressing low turnover from Medicaid to the Marketplace remains critical, improvements in turnover do not solve care continuity challenges if clinician network overlap is not also addressed. State and federal governments can require insurers to offer plans in Medicaid and the Marketplace, ideally with a requirement for the same clinician networks, to increase overlap and ensure care continuity.

Supplement.

Data Sharing Statement