The Complexities of Adapting and Validating a Novel Assay for Adherence Monitoring of Oral HIV Pre-Exposure Prophylactics

Abstract

Oral pre-exposure prophylaxis (PrEP) is effective in preventing HIV, but its efficacy depends on adherence. The gold standard for adherence monitoring, liquid chromatography-mass spectrometry, is accurate but costly and complex. Therefore, a simpler method is needed. The REverSe TRanscrIptase Chain Termination (RESTRICT) assay measures oral PrEP drug levels in blood by detecting tenofovir-diphosphate, an active PrEP metabolite. RESTRICT has a turnaround time of under 24 hours, is easy to prepare, and uses standard clinical lab equipment. The dose-dependent normalized fluorescence result can be plotted as a standard curve for semi-quantitative adherence measurement. The assay must be validated as a Laboratory Developed Test, assessing sensitivity, specificity, accuracy, precision, range, linearity, and interference. The validation showed RESTRICT as a promising alternative to mass spectrometry, potentially improving PrEP uptake and adherence.