title: Comparison of pharmacy-based measures of adherence to antiretroviral therapy as predictors of virological failure.
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.affiliation: Department of Epidemiology, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, cehenegar@gmail.com.
authors.forename: Cassidy E
authors.initials: CE
authors.lastname: Henegar
authors.forename: Daniel
authors.initials: D
authors.lastname: Westreich
authors.forename: Mhairi
authors.initials: M
authors.lastname: Maskew
authors.forename: M Alan
authors.initials: MA
authors.lastname: Brookhart
authors.forename: William C
authors.initials: WC
authors.lastname: Miller
authors.forename: Pappie
authors.initials: P
authors.lastname: Majuba
authors.forename: Annelies
authors.initials: A
authors.lastname: Van Rie
mesh_terms: D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D003625:Data Collection; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010594:Pharmacies; D013019:South Africa; D017211:Treatment Failure; D019562:Viral Load; D016903:Drug Monitoring