Adherence and virologic suppression during the first 24 weeks on antiretroviral therapy among women in Johannesburg, South Africa - a prospective cohort study

Background: Adherence is a necessary part of successful antiretroviral treatment (ART). We assessed risk factors for incomplete adherence among a cohort of HIV-infected women initiating ART and examined associations between adherence and virologic response to ART. Methods: A secondary data analysis was conducted on a cohort of 154 women initiating non-nucleoside reverse transcriptase inhibitor (NNRTI)-based ART at a single site in Johannesburg, South Africa. Ninety women had been enrolled in a prevention of mother-to-child transmission (pMTCT) program and were exposed to single-dose nevirapine (sdNVP) > 18 months earlier. Women were interviewed pre-treatment and clinical, virologic and adherence data were collected during follow-up to 24 weeks. Incomplete adherence to ART was defined as returning > 5% of medications, estimated by pill counts at scheduled visits. Multivariable logistic regression analysis and unadjusted odds ratio (95%CI) were performed, using STATA/SE (ver 10.1). Results: About half of the women (53%) were < 30 years of age, 63% had < 11 years of schooling, 69% were unemployed and 37% lived in a shack. Seven percent of women had a viral load > 400 copies/ml at 24 weeks and 37% had incomplete adherence at one or more visits. Incomplete adherence was associated with less education (p = 0.01) and lack of financial support from a partner (p = 0.02) after adjustment for confounders. Only when adherence levels dropped below 80% was there a significant association with viremia in the group overall (p = 0.02) although adherence < 95% was associated with viremia in the sdNVP-exposed group (p = 0.03). The main reasons for incomplete adherence were being away from home, busy with other things and forgetting to take their medication. Conclusion: Virologic response to NNRTI-treatment in the cohort was excellent. However, women who received sdNVP were at greater risk of virologic failure when adherence was < 95%. Women exposed to sdNVP, and those with less education and less social support may benefit from additional adherence counseling to ensure the long-term success of ART. More than 80% adherence may be sufficient to maintain virologic suppression on NNRTI-based regimens in the short-term, however complete adherence should be encouraged.