The Role of Medicaid HMO Enrollment in the Longitudinal Utilization of Medical Care Services in a Cohort of Injecting Drug Users in Baltimore, Maryland

Although injecting drug users (IDUs) are highly dependent on Medicaid, the literature has not explored the effect of Medicaid HMO enrollment on medical care utilization. This longitudinal analysis compares 6-month utilization levels of IDUs in Medicaid HMOs with those of other Medicaid-enrolled IDUs and IDUs in other insurance arrangements. The analysis includes 1064 participants from the AIDS Link to Intravenous Experience (ALIVE) study, a natural history study of HIV infection in a community-based sample of IDUs in Baltimore, Maryland. A generalized linear modeling approach was used to examine self-reported inpatient admissions, ER visits, and ambulatory care visits from January 1995 through June 1997. Non-HMO Medicaid beneficiaries had more inpatient admissions and ambulatory care visits than Medicaid HMO enrollees. These findings suggest that HMO enrollment has been effective in lowering utilization among IDUs in Medicaid, but it is unclear whether utilization differences are the result of inappropriate utilization or access issues.