Clinical and Economic Outcomes of Nonadherence to Highly Active Antiretroviral Therapy in Patients with Human Immunodeficiency Virus

Background: Nonadherence with highly active antiretroviral therapy (HAART) is common in typical human immunodeficiency virus (HIV) patient care settings, but the consequences have not been well described. This study aimed to quantify the clinical and economic effects of nonadherence and estimate the cost-effectiveness of improving adherence in treatment-naive HIV patients.

Methods: A Markov model was developed to project quality-adjusted life expectancy and direct medical costs for patients on an initial once-daily regimen of efavirenz, lamivudine, and stavudine XR. The model compared 2 adherence scenarios: "ideal" (based on clinical trials) and "typical" (based on observational studies in actual practice). Disease progression was a function of viral load, CD4 count, and adherence. Data on HIV natural history, treatment benefits, costs, and utilities were derived from the literature.

Results: With typical adherence, patients lose 1.2 quality-adjusted life years (QALYs) that could be gained with ideal adherence. Improving adherence to ideal levels is cost-effective at 29,400 US dollars/QALY gained. As much as 1,600 US dollars/y per patient could be spent on an intervention to improve adherence to ideal levels, and the incremental cost-effectiveness would remain less than 50,000 US dollars/QALY gained. A cost-effectiveness ratio of 50,000 US dollars/QALY is a commonly accepted minimum standard for cost-effective medical interventions in the United States, although many experts believe this standard has drifted upwards over time.

Conclusions: Typical adherence with HAART reduces quality-adjusted life expectancy by 12% compared with ideal adherence. Interventions to improve adherence appear to be a highly cost-effective use of resources.