A longitudinal evaluation of the effect of Medi-Cal managed care on supplemental security income and aid to families with dependent children enrollees in two California counties.

OBJECTIVE: We examined the differential effect of Medicaid managed care (MMC) among Aid to Families With Dependent Children (AFDC) and Supplemental Security Income (SSI) enrollees over time by comparing the experiences of adult nonelderly enrollees in the Health Plan of San Mateo in California versus Ventura County's fee-for-service (FFS) enrollees.

RESEARCH DESIGN: Four years of administrative claims data were used to construct a longitudinal data set and estimate panel data models to decompose the effect of managed care over time.

RESULTS: AFDC MMC enrollees exhibited generally fewer ambulatory visits, lower expenditures, and higher monthly probabilities of a preventable hospitalization relative to comparably enrolled FFS patients. SSI MMC enrollees had more emergency department visits and higher monthly probabilities of hospitalization. However, SSI MMC enrollees had more ambulatory visits and more medications during the first year of enrollment relative to SSI FFS enrollees, although levels were similar in subsequent years. SSI MMC enrollees did not exhibit a significantly higher level of expenditures in the first year of enrollment, although in subsequent years, expenditure levels were significantly lower.

CONCLUSIONS: The results for emergency department visits and preventable hospitalizations presented a decidedly downbeat picture of access to care for AFDC and SSI enrollees in MMC. However, some aspects of utilization under managed care exhibited results consistent with long-term- oriented treatment for enrollees with a greater likelihood of remaining in the system for a longer period of time (SSI enrollees). By contrast, enrollees more likely to be enrolled for shorter periods (AFDC enrollees) tended to exhibit care patterns under MMC consistent with lower levels of care relative to FFS.