Can accountable care divert the sources of hospitalization?

OBJECTIVES: To examine the impact of coordinated care organizations (CCOs), Oregon's Medicaid accountable care organizations, on hospitalization by admission source among female Medicaid beneficiaries of reproductive age. STUDY DESIGN: We employed a difference-in-differences (DID) approach, capitalizing on the fact that CCO enrollment was generally mandatory whereas some Medicaid beneficiaries were exempt. METHODS: We used 2011-2013 Oregon Medicaid eligibility files linked to hospital discharge data and birth certificates. We constructed person-month panel data on 86,012 women aged 15 to 44 years (N = 2,705,543 observations) who were continuously enrolled in Oregon Medicaid. Outcomes included total and preventable hospital admissions. We also examined admissions separately by source, including scheduled and unscheduled admissions, as well as admissions through the emergency department. We estimated a fixed-effects multivariate DID model that compared a change in each outcome before and after CCO enrollment for CCO-enrolled Medicaid beneficiaries with a pre–post change for other Medicaid beneficiaries not enrolled in CCOs throughout the study period. RESULTS: Hospitalization rates decreased overall for female Medicaid beneficiaries enrolled in CCO and also for non-CCO enrollees, whereas the proportions of unscheduled and preventable admissions increased for both Medicaid subgroups. CCO enrollment was significantly associated with a decline of one-fourth from the pre-CCO average in the probability of all-source preventable hospitalization, largely due to a decline in unscheduled preventable admissions. CONCLUSIONS: CCO led to reductions in hospital admissions, especially preventable admissions, among female Medicaid beneficiaries of reproductive age in Oregon. Findings, if replicated, may imply that the accountable care delivery model implemented in Oregon Medicaid promotes efficient resource utilization.