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Simple assessments of adherence to antiretroviral therapy predict virologic failure in HIV infected patients in Lusaka, Zambia
Presented by Ronald A. Cantrell, Zambia.
Goldman J.D.1, Mumba P.1, Cantrell R.A.1, Levy J.1, Limbada M.1, Morris M.1, Mulenga L.1, Reid S.1, Chisembele Taylor A.1, Chi B.H.1, Vermund S.H.2, Stringer J.S.A.1
1University of Alabama at Birmingham, Center for Infectious Disease Research Zambia, Lusaka, Zambia, 2Vanderbilt University School of Medicine, Institute for Global Health, Nashville, United States
Objectives: In resource-limited settings, evaluation of adherence to antiretroviral therapy (ART) is critical given the poor availability of routine viral load (VL) testing and limited options for second-line therapy. We evaluated the association of adherence measurements with virologic failure in Lusaka, Zambia.
Methods: In the ART program, patients receive monthly dispensations of drugs and are followed in a computerized database. Patients in this analysis were on ART > 100 days before treatment failure was suspected. Virologic suppression was defined as < 400 copies/mL. Adherence measures included days late for monthly pharmacy visits averaged over the course of treatment and patient self-report of missed doses three days prior to pharmacy visits.
Results: 124 of 415 patients tested (30%) had detectable VL. The median time from ART initiation to VL measurement was 602 (IQR = 439–750) days. Median number of days late per month was 0.9 (IQR = 0.2–2.2) for suppressed patients vs. 1.6 (IQR = 0.5–3.0) for non-suppressed patients (p<0.01). Compared to those who were never late for pharmacy pick-ups, the risk of detectable VL was higher among those who were below the median of 1.0 day late per month (RR=1.9; 95%CI = 0.99–3.5); those between the median and the 90%tile of 4.2 days late per month (RR=2.2; 95%CI = 1.2–4.0); and those above the 90%tile (RR=3.1; 95%CI = 1.6–5.9). These findings held after adjusting for age, baseline hemoglobin and baseline CD4. Only 76 patients (22%) reported missing one or more doses of ART and these patients were at higher risk for virologic failure (RR = 1.5; 95%CI = 1.1–2.1).
Conclusions: The degree of lateness for pharmacy refills correlates in a dose response relationship with virologic failure. While few people reported missing ART doses, those with positive responses were more likely to have detectable viral load.
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