National estimates of the effects of mandatory Medicaid managed care programs on health care access and use, 1997-1999.

Objective: We sought to explore how mandatory Medicaid managed care programs affect access to care and use among full-year Medicaid beneficiaries not receiving SSI or Medicare.

Research Design: We used data from the 1997 and 1999 National Survey of America's Families. To establish what Medicaid beneficiaries' access and use would have been in the absence of Medicaid managed care (MMC) and to control for unobserved county differences, we estimated difference-in-difference models using a comparison group of privately insured individuals who we would not expect to be affected by MMC.

Results: We found weaker effects of MMC programs for children than adults. The strongest result is that mandatory HMO programs lower the probability of Medicaid adults using emergency rooms, when implemented alone or in combination with Primary Care Case Management (PCCM) programs. PCCM programs reduced the number of visits among adults but had little effect on other measures of access and use. There was less preventive care in mandatory HMO counties for women, suggesting that the federally required external quality review may be appropriate.

Conclusion: The effects of Medicaid managed care vary with the type of program, and policy makers should not expect programs that rely on PCCMs to have the same effects as those that incorporate mandatory HMO enrollment. Moreover, none of the program models had strong and consistent effects across the indicators of access and use that we considered.