The impact of Medicaid managed care on hospitalizations for ambulatory care sensitive conditions.

OBJECTIVE: To determine whether Medicaid managed care is associated with lower hospitalization rates for ambulatory care sensitive conditions than Medicaid fee-for-service. We also explored whether there was a differential effect of Medicaid managed care by patient's race or ethnicity on the hospitalization rates for ambulatory care sensitive conditions.

DATA SOURCES/STUDY SETTING: Electronic hospital discharge abstracts for all California temporary assistance to needy families (TANF)-eligible Medicaid beneficiaries less than age 65 who were admitted to acute care hospitals in California between 1994 and 1999.

STUDY DESIGN: We performed a cross-sectional comparison of average monthly rates of admission for ambulatory care-sensitive conditions among TANF-eligible Medicaid beneficiaries in fee-for-service, voluntary managed care, and mandatory managed care.

DATA COLLECTION/EXTRACTION METHODS: We calculated monthly rates of ambulatory care-sensitive condition admission rates by counting admissions for specified conditions in hospital discharge files and dividing the monthly count of admissions by the size of the at-risk population derived from a separate monthly Medicaid eligibility file. We used multivariate Poisson regression to model monthly hospital admission rates for ambulatory care-sensitive conditions as a function of the Medicaid delivery model controlling for admission month, admission year, patient age, sex, race/ethnicity, and county of residence.

PRINCIPAL FINDINGS: The adjusted average monthly hospitalization rate for ambulatory care-sensitive conditions per 10,000 was 9.36 in fee-for-service, 6.40 in mandatory managed care, and 5.25 in voluntary managed care (p<.0001 for all pairwise comparisons). The difference in hospitalization rates for ambulatory care sensitive conditions in Medicaid fee-for-service versus managed care was significantly larger for patients from minority groups than for whites.

CONCLUSIONS: Selection bias in voluntary Medicaid managed care programs exaggerates the differences between managed care and fee-for-service, but the 33 percent lower rate of hospitalizations for ambulatory care sensitive conditions found in mandatory managed care compared with fee-for-service suggests that Medicaid managed care is associated with a large reduction in hospital utilization, which likely reflects health benefits. The greater effect of Medicaid managed care for minority compared with white beneficiaries is consistent with other findings that suggest that managed care is associated with improvements in access to ambulatory care for those patients who have traditionally faced the greatest barriers to health care.