Testing for tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) can be used to predict drug adherence and efficacy of pre-exposure prophylaxis (PrEP), it has not previously been used to monitor HIV treatment. The authors collected DBS up to 3 times over 48 week in patients infected with HIV being treated with tenofovir disoproxil fumarate (TDF)-based therapy. 1199 DBS were collected from 532 patients (76 female, 101 black, 101 Hispanic). Among the virologically-suppressed patients at baseline (n=347), TFV-DP was significantly lower in blacks (1453) vs. whites (1793), and vs. Hispanics (1760). It was also significantly lower in non-boosted (1610) vs. boosted (1888) regimens, and in NNRTI-based (1563) vs. boosted PI-based (1890), and multiclass-based (1927) regimens. The adjusted odds ratio (aOR) of virologic suppression (after adjusting for age, gender, race, BMI, eGFR, CD4+ T cell count, antiretroviral drug class and duration of therapy) was 73.5 (95%CI 25.7–210.5) for a TFV-DP concentration ≥1850 fmol/punch compared to <350 fmol/punch. Therefore TFV-DP in DBS is strongly associated with virologic suppression in HIV-infected patients on TDF-based therapy.
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