Point-of-care semiquantitative test for adherence to tenofovir alafenamide or tenofovir disoproxil fumarate

Objective: Objective measurement of antiretrovirals may aid clinical interventions for improving adherence to HIV prevention or treatment regimens. A point-of-care urine test could provide real-time information about recent adherence to regimens containing tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide (TAF). We developed a lateral flow immunoassay (LFA) and enzyme-linked immunoassay (ELISA) for urinary tenofovir. Methods: Intensity of the LFA test line was quantified using an optical reader and visually scored 0 - 5 by two independent people, using a reference card. The sensitivity and specificity of both the ELISA and LFA were determined for two different tenofovir concentration cutoffs for TDF and TAF adherence-1,500 ng/mL and 150 ng/mL, respectively. To validate the assays, we measured 586 urine samples from 28 individuals collected as part of a study of tenofovir pharmacokinetics in adults, which were also measured by mass spectrometry as ground truth. Results: Both the LFA signal and ELISA signal were each strongly correlated to drug concentrations (0.91 and 0.92 respectively). The LFA signal and ELISA were highly sensitive and specific at both thresholds (LFA se/sp TDF 89%/96%, TAF 90%/96%; ELISA se/sp TDF 94%/94%, TAF 92%/84%). Visual scoring of the LFA was also highly sensitive and specific at both the TDF and TAF thresholds (se/sp TDF 91%/94%, TAF 87%/90%). Conclusions: Our rapid semi-quantitative test can measure TFV concentrations relevant to both TAF or TDF adherence, which may support adherence-promoting interventions across a range of HIV care settings.