Comparison of pharmacy-based measures of adherence to antiretroviral therapy as predictors of virological failure.

Journal: AIDS And Behavior
Published:
Abstract

We compared multiple pharmacy refill-based adherence indicators for antiretroviral therapy, as well as thresholds for defining non-adherent behavior, based on ability to predict virological failure. A total of 29,937 pharmacy visits with corresponding viral load assessments were contributed by 8,695 patients attending a large clinic in Johannesburg, South Africa. Indicators based on pill coverage and timing of refill pickup performed comparably using the strictest thresholds for adherence [100 % pill coverage: odds ratio (OR) (95 % confidence interval (CI)) : 1.26 (1.15, 1.39); prescription picked up on or before scheduled refill date: 1.27 (1.16,1.38)]. For both types of indicators, the association between non-adherence and virological failure increased as the threshold defining adherent behavior was lowered. All measures demonstrated high specificity (range 84-98 %), but low sensitivity (5-19 %). In this setting, patients identified as non-adherent using pharmacy-based indicators are likely correctly classified and in need of interventions to improve compliance. Pharmacy based measures alone, however, are inadequate for identifying most cases of nonadherence.

Authors
Cassidy Henegar, Daniel Westreich, Mhairi Maskew, M Brookhart, William Miller, Pappie Majuba, Annelies Van Rie