Adherence to highly active antiretroviral therapy impact on clinical and economic outcomes for Medicaid enrollees with human immunodeficiency virus and hepatitis C coinfection.

We examined the impact of antiretroviral treatment adherence among hepatitis C (HCV) coinfected human immunodeficiency virus (HIV) patients on survival and clinical outcomes. We analyzed Medicaid claims data from 14 southern states from 2005 to 2007, comparing survival and clinical outcomes and cost of treatment for HIV and HCV coinfected patients (N = 4115) at different levels of adherence to antiretroviral therapy (ART). More than one in five patients (20.5%) showed less than 50% adherence to antiretroviral treatment, but there were no racial/ethnic or gender disparities. Significant survival benefit was demonstrated at each incremental level of adherence to ART (one-year mortality ranging from 3.5% in the highest adherence group to 26.0% in the lowest). Low-adherence patients also had higher rates of hospitalization and emergency department visits. Relative to patients with high (>95%) ART adherence, those with less than 25% treatment adherence had fourfold greater risk of death (adjusted odds ratio 4.22 [95% CI: 3.03, 5.87]). Nondrug Medicaid expenditures were lower for high-adherence patients, but cost of medications drove total Medicaid expenditures higher for high-adherence patients. Cost per quality-adjusted life year (QALY) saved (relative to the <25% low-adherence group) ranged from $21,874 for increasing adherence to 25-50% to $37,229 for increasing adherence to 75-95%. Adherence to ART for patients with HIV and HCV coinfection is associated with lower adverse clinical outcomes at a Medicaid cost per QALY commensurate with other well-accepted treatment and prevention strategies. Further research is needed to identify interventions which can best achieve optimal ART adherence at a population scale.