Novel application of dried blood spot tenofovir diphosphate to predict viral suppression in postpartum women with HIV in Malawi.

OBJECTIVE

Investigate whether antiretroviral metabolites tenofovir-diphosphate (TFVdp) and lamivudine triphosphate (3TCtp) in dried blood spots (DBS) are reliable markers of ART adherence by predicting viral suppression in postpartum women with HIV in resource-limited settings.

DESIGN

Prospective cohort study.

METHODS

Pregnant women diagnosed with HIV who started ART from October 2018- July 2021 and participated in a video-based intervention trial were included in this substudy. Whole blood samples were collected 12 months after ART initiation to measure viral load, TFVdp, and 3TCtp. Ability of TFVdp and 3TCtp to identify HIV-suppressed women was assessed using area under the curve (AUC) in receiver operating characteristic (ROC) analysis and compared to self-reported adherence data.

RESULTS

We included 588 women, with a mean age of 27 years. TFVdp and 3TCtp concentrations were detected in 82% (482/588) and 77% (455/588) of samples, respectively. Daily TFVdp dosing concentrations (≥1400 fmol/punch) were observed in 389 women of whom 86% (333/389) were HIV suppressed compared with only 22% (28/128) in those taking fewer than two doses per week; similar results were observed for 3TCtp [TFVdp odds ratio (OR) = 21.2, 95% confidence interval (CI): 12.8-35.2; 3TCtp OR = 7.5, 95% CI: 3.7-15.3]. ROC analysis revealed identical AUCs of 0.83 (95% CI: 0.78-0.87) for both metabolites, which was significantly higher than the AUC for self-reported adherence data (0.58, 95% CI: 0.53-0.63). Approximately one-third of women had TFVdp levels >2800 fmol/punch, which was higher than expected for daily dosing.

CONCLUSIONS

TFVdp and 3TCtp concentrations measured in DBS samples are reliable markers of ART adherence and outperform self-reported adherence data. High TFVdp levels warrant further investigations.