High adherence to oral daily PrEP in a real-world implementation project in Kenya: a brief communication

Objective biomarkers of oral pre-exposure prophylaxis (PrEP), such as tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), remain critical for interpreting PrEP adherence. We tested 195 DBS randomly collected from 168 of 4,955 PrEP clients returning for refills at 25 public HIV clinics in Kenya. DBS were extracted using the 50:50 methanol: water method, and drug concentrations quantified using liquid chromatography-tandem mass spectrometry. Optimal adherence was defined as ≥ 900 fmol/punch, corresponding to ≥ 4 doses/week. TFV-DP was detectable in 96% (188/195) of samples; 71% (138/195) had optimal adherence, higher among older clients and men. Optimal adherence is achievable in real-world PrEP programs.