Protection From HIV With Pre-Exposure Prophylaxis May be Accurately Assessed in Urine Samples

Urine tenofovir (TFV) levels may be an adequate assessment of persistence and protection against HIV from pre-exposure prophylaxis (PrEP). These findings, from a nested cohort study, were published in Clinical Infectious Diseases.

Couples who were HIV serodiscordant were recruited from Kenya and Uganda for the Partners PrEP Study. Participants were randomized to receive either tenofovir disoproxil fumarate (TDF) with emtricitabine or TDF only. Urine and blood samples were collected at months 3, 12, 24, and 36 and assessed for TFV. This analysis included a subset of 292 of the study participants.

Study participants were 39% women with a median age of 33 years (interquartile range [IQR], 28-39). During the study, 52 participants developed HIV while on PrEP. These participants were 55% women aged median 33 (IQR, 27-39) years.

TFV concentration in urine samples was a median of 37,500 ng/mL (IQR, 500-90,000) and in plasma was a median of 65.4 ng/mL (IQR, 1.6-103.0). TFV concentrations in urine and blood were moderately correlated (r, 0.46; P <.001).

Among 558 samples with TFV of at least 0.30 mg/mL in the plasma, 486 samples had a paired urine TFV of at least 1000 ng/mL (sensitivity, 87%; 95% CI, 84-90%). The 468 samples with TFV greater than 40 ng/mL had paired urine samples with TFV of at least 1500 ng/mL (n=420; sensitivity, 90%; 95% CI, 87-92%). Among samples with undetectable TFV (n=164), many also had undetectable urine TFV (n=119; specificity, 73%; 95% CI, 65%-79%).

Participants on PrEP who had urine TFV concentrations of at least 1500 ng/mL had a 71% reduced risk (95% CI, 30%-88%; P =.006) and those with plasma TFV concentrations great than 40 ng/mL had an 87% reduced risk (95% CI, 54%-96%) for HIV infection after adjusting for age, gender, and occurrence of unprotected sex.

This study may have been biased by the long-term storage of urine samples, which may have caused some sample degradation.

This study suggested that urine monitoring of TFV concentrations may be an adequate assessment of PrEP usage and protection against HIV infection.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Stalter R M, Baeten J M, Donnell D, et al. Urine tenofovir levels measured using a novel immunoassay predict human immunodeficiency virus protection. Clin Infect Dis. 2021;72(3):486-489. doi:10.1093/cid/ciaa785.