Care of Patients With Chronic Conditions and Clinician Participation in Accountable Care Organizations

To compare chronic condition specialists to primary care providers (PCPs) on rates of serving as the usual provider of care (UPC, defined as providing the most visits) versus being accountable under "PCP-first" assignment used in accountable care organization (ACO) programs, and to compare risk-based ACO participation.

We conducted a retrospective cohort study of PCP versus chronic condition specialty clinicians on their rates of serving as UPC for patients with complex chronic conditions, patient assignment under a "PCP-first" assignment mechanism, and participation in risk-based ACOs. We then estimated linear probability models predicting clinician participation in risk-based ACOs as a function of their rates of serving as the UPC.

We used 100% traditional fee-for-service Medicare (TM) clinician data and beneficiary claims from 2017 to 2022.

The study included 2,065,755 and 254,918 clinician-years for PCPs and chronic condition specialists (cardiology, endocrinology, nephrology, pulmonology), respectively. Specialists more often served as the UPC than they were accountable under PCP-first assignment algorithms (7.9% UPC vs. 3.3% PCP-first assignment); the opposite was true of PCPs (19.2% vs. 29.8%). Specialists in the top quintile for serving as UPC were 19.0% less likely (4.4 percentage point [pp] absolute difference, 95% CI, 3.7-5.1 pp) to participate in risk-based ACOs than specialists in the bottom quintile. PCPs in the top UPC quintile were 18.7% more likely (3.8 pp. absolute difference, 95% CI, 3.6-4.1 pp) to participate in risk-based ACOs than PCPs in the bottom quintile.

Existing assignment mechanisms in Medicare ACOs may undervalue specialists' care for patients with chronic conditions. More efforts are needed to engage specialists in accountable care.