BACKGROUND: Electronic adherence (EA) and tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) are objective measures of antiretroviral therapy (ART) adherence. We characterized the association between these measures in a prospective cohort of persons with HIV (PWH) on ART.
SETTING: Four primary health clinics in Cape Town, South Africa.
METHODS: We enrolled 250 virally suppressed PWH receiving tenofovir-based ART. We collected EA data, monthly viral load and TFV-DP in DBS for 12 months. We used logistic regression to estimate the adjusted odds ratio (aOR) and 95% confidence intervals (CI) for future viral breakthrough (VB) (>400 copies/mL) for each adherence measure. Receiver Operating Characteristics (ROC) provided the predictive power of these measures.
RESULTS: Participants had a median (IQR) age of 34 (27-42); 78% were women. Twenty-one (8%) developed VB. Logistic regression showed that when percent EA and TFV-DP concentrations increased, the odds of VB decreased. This relationship was consistent at the time of VB (aOR of 0.41 [95% CI 0.25-0.66] for TFV-DP and aOR of 0.64 [95% CI 0.54-0.76] for EA) and for up to two months prior to VB. Both adherence measures predicted future VB at both one month and two months prior to viral load measurement.
CONCLUSION: We established that two objective adherence measures, EA and TFV-DP in DBS, have a positive association with, and are both strongly predictive of, VB in a community-based South African cohort on ART. Future research is needed to determine the feasibility of implementing these adherence measures in resource-limited settings to facilitate adherence interventions.
Comparing predictive ability of two objective adherence measures in a community-based cohort on antiretroviral therapy in South Africa: Tenofovir diphosphate concentrations and electronic adherence monitors
Journal of Acquired Immune Deficiency Syndromes, 93 (4), 327-332. doi: 10.1097/QAI.0000000000003198. PMCID: PMC10287050.