Costs to Medicaid of Advancing Immunosuppression in an Urban HIV-Infected Patient Population in Maryland

Abstract

Human immunodeficiency virus (HIV) infection is increasingly an urban disease in the United States, and Medicaid is the principal payer of the health care costs of patients with HIV. We wished to determine the costs to Medicaid of patients in Maryland infected with HIV as immunosuppression progresses, and to determine how costs varied by demographic characteristics of the patient. We analyzed combined economic and clinical data in patients from the Johns Hopkins HIV Service, the provider of primary and specialty care for a majority of HIV-infected patients in the Baltimore metropolitan region. All patients were enrolled in Medicaid and received care longitudinally in Maryland from July 1992 to June 1995. Monthly Medicaid payments were calculated for all inpatient and outpatient services by sex, race, age, use of injecting drugs, CD4⁺ count (>500, 201-500, 51-200, ≤50 cells/mm³), several opportunistic diseases, and death. Lifetime costs were also calculated by use of a Markov simulation. During 13,174 person-months of follow-up in 606 patients, a total of $18,223,700 in Medicaid payments was made. Mean monthly payments ranged from $2,436 (SE $171) for patients with CD4⁺ counts ≤50 cells/mm³ to$1,015 (SE $177) for patients with CD4⁺ counts >500 cells/mm³. Mean monthly inpatient costs ranged from $1,355 (SE $131) for CD4⁺ counts≤50 cells/mm³ and $617 (SE $164) for CD4⁺ counts >500 cells/mm³. For those with CD4⁺ counts ≤50 cells/mm³, outpatient pharmacy costs averaged $515 (SE$57) monthly, second only to inpatient costs. In bivariate analysis, costs were significantly higher (p = .013) in men (mean $1696; SE $126) than in women (mean$1,208; SE $101), though the difference was not significant with multivariate adjustment. Cytomegalovirus retinitis was the most costly opportunistic disease, with mean monthly costs of $7,825 (SE $1,141) within the 6 mo after diagnosis. Within 6 mo of death, mean monthly costs are $4,600 (SE $424). Lifetime costs for treating an HIV-infected patient who presents with a CD4⁺ count >500 cells/mm³ are $133,500 over 8.3 years of life. We concluded that in the clinic where the analysis was done, average costs to Medicaid of treating patients increase more than two-fold as the CD4⁺ count declines from >500 cells/mm³ to ≤50 cells/mm³. Interventions that decrease hospitalization, opportunistic disease, and the costs of terminal care may be most likely to decrease overall costs. Demographic patient characteristics do not affect costs significantly when access to care is comparable.