Acceptability and Feasibility of Providing Adherence Feedback Based on Tenofovir Diphosphate in Dried Blood Spots: Results from a Pilot Study Among Patients and Providers in Cape Town, South Africa

Tenofovir diphosphate (TFV-DP) concentrations in dried blood spots (DBS) predict viral breakthrough, but their use remains understudied in real-world clinic settings. This pilot study examined acceptability, feasibility, and initial adherence outcomes of providing adherence feedback using TFV-DP concentrations on patient- and provider-levels in Cape Town, South Africa. We enrolled 60 persons with HIV (PWH) receiving tenofovir-containing ART attending a primary health clinic. They were randomized 1:1 to an intervention receiving TFV-DP concentration feedback by research staff vs. no feedback at monthly visits for 4 months. Acceptability among medical providers and level of clinical follow-up of TFV-DP results was examined. Patient acceptability was assessed descriptively. Mean electronic adherence (EA), as measured by WisePill device, and TFV-DP in DBS were compared between the two arms. All participants in the intervention group (100%) reported finding TFV-DP feedback helpful and 86% reported changing adherence behaviors. Medical providers indicated high acceptability of incorporating TFV-DP concentration feedback into the clinic, yet among 29 results < 1000 fmol/punch, only 2 were reviewed with no follow-up actions performed. In the intervention arm, mean TFV-DP concentrations were significantly higher (t = 2.5, p <.01) during follow-up and EA in upper quartile (96–100%) was greater compared to controls (x2 = 7.8, p ≤.05). This study found high acceptability among patients for receiving adherence feedback based on TFV-DP concentrations. TFV-DP and EA data demonstrated greater adherence in the intervention group. Providers indicated high acceptability of incorporating TFV-DP feedback into the clinic, but few providers reviewed results, which could impact clinic-level feasibility.