Assessing the utility of a community pharmacy refill record as a measure of adherence and viral load response in patients infected with human immunodeficiency virus

Study Objective. To assess the utility of a community pharmacy refill record as a measure of adherence to antiretroviral agents and as a predictor of viral load response. Design. Retrospective review of laboratory and community pharmacy records. Setting. University-based human immunodeficiency virus (HIV) clinic and local community pharmacy. Patients. Ninety-four patients with HIV or the acquired immunodeficiency syndrome (AIDS) who visited both settings and had retrievable pharmacy and laboratory records. Measurements and Main Results. Community pharmacy records were compiled and screened for antiretroviral agent refill histories. The continuous, multiple-interval measure of medication gaps (CMG), a measure of drug nonadherence, was calculated for each antiretroviral agent. Viral load information was retrieved from the clinic records of patients who had a community pharmacy refill record documenting the previous 2 years. As refill nonadherence increased, viral load response increased, following an approximately sigmoid relationship. When the CMG score was less than 0.10, the viral load response did not change appreciably. The steepest rise in viral load response occurred with a CMG score ranging from 0.10- 0.19. For values of 0.20 or greater, the viral load response was less sensitive to adherence performance. The probability (i.e., sensitivity) of having at least a 10% nonadherence record given a viral load greater than 1000 copies/ml was 80%. Conclusion. The community pharmacy refill record is a convenient, accessible, and useful tool for assessing adherence and predicting viral load outcomes in patients with HIV and AIDS.