OBJECTIVES: Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is used as a biomarker of ART adherence. Recent treatment studies have shown that TFV-DP predicts future viremia in persons with HIV (PWH) but there are few data from high-burden settings. We investigated whether TFV-DP in DBS predicts future viral breakthrough in South African PWH.
DESIGN: Prospective observational cohort.
METHODS: We enrolled 250 adults receiving tenofovir-containing regimens, currently virally suppressed (<50 copies/mL), but at risk of future viral breakthrough, from four primary health clinics in Cape Town. Paired viral load (VL) and DBS for TFV-DP were collected monthly for 12 months. Viral breakthrough was the first confirmed VL >400 copies/mL. Logistic regression estimated the odds ratio (OR) and 95% confidence intervals for future viral breakthrough at the next visit.
RESULTS: Participants provided 2,944 paired DBS and VL samples. Median (IQR) age was 34 (27 – 42) years; median duration on ART at study entry was 11 (4-12) months; 78% were women. Twenty-one (8%) participants developed viral breakthrough. Participants with TFV-DP 800 fmol/punch.
CONCLUSIONS: TFV-DP in DBS strongly predicted future viral breakthrough in a clinical cohort of South African PWH. A biomarker able to identify PWH at risk for future viral breakthrough has the potential to improve health outcomes through timely intervention. Future studies exploring the clinical use of TFV-DP in DBS in conjunction with viral load in ART monitoring are warranted.
Tenofovir diphosphate in dried blood spots predicts future viremia in persons with HIV taking antiretroviral therapy in South Africa
AIDS, 36 (7), 933-940. doi: 10.1097/QAD.0000000000003185. PMCID: PMC9167214.