To explore the cost-effectiveness of interventions to improve adherence to combination antiretroviral therapy in patients with human immunodeficiency virus (HIV) infection.

A simulation model of HIV infection, incorporating CD4 cell count and HIV ribonucleic acid levels as predictors of disease progression, was used to estimate the lifetime costs and quality-adjusted life expectancy associated with clinical interventions to improve adherence to antiretroviral therapy (e.g., directly observed therapy, automatic medication dispensers, beepers, portable alarms) in a clinical trial cohort with early disease (mean CD4 count, 350 cells/μL), a clinical trial cohort with advanced disease (mean CD4 count, 87 cells/μL), and an urban cohort (mean CD4 count, 217 cells/μL). Data were from clinical trials, national databases, and published literature.

For relatively healthy patients with early disease, interventions that reduced virologic failure rates by 10% increased quality-adjusted life expectancy by 3.2 months, whereas those that reduced failure by 80% increased quality-adjusted life expectancy by 34.8 months, as compared with standard care. The cost-effectiveness ratio was below $50,000 per quality-adjusted life-year (QALY) for interventions costing $100 per month provided that failure rates were reduced by at least 10%, and for those costing $500 per month provided that failure rates were reduced by more than 50%. For both patients with advanced disease and those from an urban cohort, adherence interventions costing about $500 per month (e.g., directly observed therapy) had to reduce failure by about 25% to have cost-effectiveness ratios below $50,000 per QALY.

In patients with lower baseline levels of adherence or advanced disease, even very expensive, moderately effective adherence interventions are likely to confer cost-effectiveness benefits that compare favorably with other interventions.