Performance of a whole blood immunoassay for tenofovir detection and correlation with self-reported pre-exposure prophylaxis use in HIV-negative men who have sex with men interested in blood donation.

Background: In 2023, the United States Food and Drug Administration revised its blood donor eligibility policy for men who have sex with men (MSM) from a 3-month deferral to individual assessment. Human Immunodeficiency Virus (HIV) pre-exposure prophylaxis (PrEP) use remains a reason for deferral, and nondisclosure is a concern.

Study design and methods: In a cross-sectional study of sexually active MSM from 8 U.S. cities who were interested in future blood donation, we assessed the performance of an enzyme-linked immunosorbent assay for detecting tenofovir (TFV) in whole blood (WB) and plasma and the correlation with self-reported PrEP use.

Results: Of 1548 individuals, 48% reported oral PrEP use. The WB assay identified 95% of PrEP users, while the plasma assay detected 88%. The WB assay performed well up to 14 days after the last reported dose. Receiver operating characteristics curve analysis showed an area under the curve of 0.96 (95% confidence interval [CI]: 0.95-0.97) using WB and 0.88 (95% CI: 0.86-0.90) using plasma. Specificity was 80% for WB and 66% for plasma. Detection rates for TFV disoproxil fumarate/emtricitabine (FTC) formulations were 99% in WB and 98% in plasma, compared to 93% and 86% for the TFV alafenamide/FTC formulation.

Discussion: High concordance between self-reported oral PrEP use and TFV detection was observed among PrEP users, suggesting the potential utility of WB as a biomatrix for TFV detection to support screening strategies. Given the expanded eligibility for MSM, who may be PrEP users, to donate blood, further examination of undisclosed PrEP use is important.