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Comparison of Pharmacy-Based Measures of Adherence to Antiretroviral Therapy as Predictors of Virological Failure

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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.

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Acknowledgments

The authors gratefully acknowledge the dedicated staff of the Themba Lethu Clinic and all clinic patients for allowing them to use their clinic data for research purposes. Clinical activities at the Themba Lethu Clinic are supported by the South African National and Gauteng provincial Department of Health, with additional funding support from the United States President’s Emergency Plan for AIDS Relief (PEPFAR) in a Grant by USAID to Right to Care and the Institution (674-A-00-08-00007-00). C.H. and D.W. received funding from the National Institute for Health Grant R00-HD-06-3961.

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Authors and Affiliations

  1. Department of Epidemiology, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    Cassidy E. Henegar, Daniel Westreich, M. Alan Brookhart & Annelies Van Rie

  2. Health Economics and Epidemiology Research Office, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa

    Mhairi Maskew

  3. Department of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    William C. Miller

  4. Right to Care, Johannesburg, South Africa

    Pappie Majuba

Authors
  1. Cassidy E. Henegar
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  2. Daniel Westreich
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  3. Mhairi Maskew
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  4. M. Alan Brookhart
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  5. William C. Miller
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  6. Pappie Majuba
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  7. Annelies Van Rie
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Correspondence to Cassidy E. Henegar.

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Henegar, C.E., Westreich, D., Maskew, M. et al. Comparison of Pharmacy-Based Measures of Adherence to Antiretroviral Therapy as Predictors of Virological Failure. AIDS Behav 19, 612–618 (2015). https://doi.org/10.1007/s10461-014-0953-2

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