Association for Public Policy Analysis & Management

Under the Patient Protection and Affordable Care Act, 37 states have expanded Medicaid to cover non-elderly adults under 138% of the federal poverty level. Prior to expansion, states had little information on the health needs of the newly eligible population on which to base enrollment and spending projections. Prior studies suggest that newly eligible enrollees are a heterogeneous group and include the long-term uninsured along with those who may have had intermittent insurance coverage. As a consequence, newly eligible enrollees are likely to use health care services in different ways, particularly in the context of emergency department (ED) care. To characterize this heterogeneity and inform efforts to increase efficiency and quality of ambulatory care, we studied the trajectories of ambulatory care visits and ED visits among Pennsylvania Medicaid expansion enrollees, a state ranking fifth in Medicaid enrollment.

We used Pennsylvania Medicaid claims and enrollment data (2015-2017) to identify subgroups based on longitudinal patterns in healthcare utilization in the first year of Medicaid enrollment for enrollees eligible under the ACA expansion. We included 601,877 enrollees ages 19-64 years who were continuously enrolled for at least 6 months as expansion enrollees (and in any enrollment category for the following six months). not dually-enrolled in Medicare, and had at least one ambulatory care or ED visit. Group-based multi-trajectory modeling was used to identify sub-groups following distinct longitudinal patterns of ED visits and ambulatory care visits. We examined the demographics, health status, and reasons for ED and ambulatory care visits of each subgroup.

We identified six unique subgroups:

• Group 1, 30% of the sample, had low stable ED use with increasing ambulatory care use;
• Group 2, 22%, had high initial ED use that declined over time and low ambulatory care use;
• Group 3, 20%, had decreasing ED and ambulatory care use;
• Group 4, 17%, had stable ED use and increasing ambulatory care use;
• Group 5, 5% had high initial ED use that declined over time and initially low but increasing ambulatory care use;
• Group 6, 5%, had high initial ED use that declined over time and very high ambulatory care use that exhibited a bell-shaped pattern.

Reasons for visiting the ED were similar across the six subgroups. However, reasons for non—ED ambulatory care use were highly variable. Among Group 6 enrollees, who had the most ambulatory care use overall, 30% of ambulatory care visits were for substance-related disorders and another 21% were for mood disorders. For Group 5 enrollees, who had the most ED visits, 11% of ambulatory care visits were dental and 11% were for mood disorders. Among the Group 1 enrollees, the plurality of ambulatory care visits were for dental care, medical evaluation, and optometry (32%).

Characterization of subgroups of Medicaid expansion enrollees that differ in service use over time informs Medicaid agencies on the health needs and services used by millions of newly publicly insured individuals. These subgroups are heterogenous and may benefit from different sets of services to reduce ED utilization and improve enrollee health.