- The tenofovir diphosphate (TFV-DP) in dried blood spots is a predictor of future viremia >20 copies/mL in persons living with HIV taking tenofovir disoproxil fumarate (TDF).
- The result is confirmed for participants virologically-suppressed at the time of the visit.
- The study shows a possible use of this adherence biomarker as a complement to HIV viral load (VL) in clinical care to monitor the efficacy of antiretroviral therapy.
TFV-DP, the phosphorylated anabolite of tenofovir, quantified in dried blood spots (DBS) was previously associated with viral suppression in persons living with HIV taking tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide. This study expands the potential clinical utility of TFV-DP and highlights the value that an objective measure of adherence could add to the information that is currently provided by HIV viral load (VL) in clinical care.
The study enrolled persons living with HIV on TDF within the University of Colorado Hospital Infectious Diseases Group Practice (Aurora, Colorado) from June 2014 to July 2017.
Blood for plasma HIV VL and TFV-DP in dried blood spots were prospectively collected (up to 3 visits within 48 weeks). The primary outcome was HIV VL. Undetectable VL was defined as
TFV-DP cut points were selected using logistic prediction models maximizing the area under the receiver operation characteristic curve.
The estimated adjusted odds ratio (aOR) of future viremia (≥20 copies/mL) were compared to the highest TFV-DP category. A total of 807 participants were enrolled and 451 participants were included in the analysis. The aOR of future viremia for participants with TFV-DP below the limit of quantification
Result was confirmed for 351 participants who were virologically-suppressed at the time of the study visit: the aOR (95% CI) for TFV-DP to
Further research to determine whether TFV-DP in DBS can improve clinical outcomes in patients on antiretroviral therapy is needed.
Limitations: the cohort was observational and the analysis did not include all patients enrolled; the predictive value of TFV-DP derived from tenofovir alafenamide-regimen was not assessed; some participants missed their 2nd or 3rd visit after enrolment; the timing between DBS and future HIV VL sampling was variable.