Tenofovir Diphosphate in Dried Blood Spots is Strongly Associated with Viral Suppression in Individuals with HIV infection.

Background. Although tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a predictor of adherence and pre-exposure prophylaxis efficacy, its utility in human immunodeficiency virus (HIV) treatment remains unknown. Methods. DBS for TFV-DP were collected up to 3 times over 48 weeks in persons living with HIV (PLWH) who were receiving TFV disoproxil fumarate (TDF)-based therapy. Log-transformed baseline TFV-DP was compared using t-tests or analyses of variance; generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression (<20 copies/mL) based on the TFV-DP concentration at the study visit. Results. We analyzed 1199 DBS from 532 participants (76 female; 101 Black, 101 Hispanic). Among the virologically-suppressed participants at baseline (n = 347), TFV-DP was lower in Blacks (geometric mean 1453, 95% confidence interval [CI] 1291-1635) vs Whites (1793, 95% CI 1678-1916; P =.002) and Hispanics (1760, 95% CI 1563-1982; P =.025); in non-boosted (1610, 95% CI 1505-1723) vs. boosted (1888, 95% CI 1749-2037; P =.002) regimens; and in non-nucleoside reverse transcription inhibitor-based (1563, 95% CI 1432-1707) vs. boosted protease inhibitor-based (1890, 95% CI 1704-2095; P =.006) and multiclass-based (1927, 95% CI 1650-2252; P =.022) regimens. The aOR of virologic suppression, after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4(+) T-cell count, antiretroviral drug class and duration of therapy, was 73.5 (95% CI 25.7-210.5; P <.0001) for a TFV-DP concentration = 1850 fmol/punch compared to < 350 fmol/punch. Conclusions. TFV-DP in DBS is strongly associated with virologic suppression in PLWH on TDF-based therapy and is associated with certain participant characteristics. Further research is required to evaluate this drug adherence and exposure measure in clinical practice.