High tenofovir diphosphate (TFV-DP) concentrations suggestive of excellent adherence to daily HIV pre-exposure prophylaxis (PrEP) were observed among men who have sex with men. Daily PrEP adherence was found to be particularly high among older individuals, those who reported condomless intercourse prior to PrEP initiation, and those who used a mobile app with visualized feedback to monitor adherence. These study results were published in Sexually Transmitted Infections.
Researchers conducted a study to explore factors associated with long-term adherence to daily PrEP. Eligible patients included MSM and transgender women at increased risk for HIV transmission who received daily prep with emtricitabine and tenofovir disoproxil. Adherence to daily PrEP was determined by measuring TFV-DP concentrations in dried blood spots that were collected at 12 and 24 months after PrEP initiation.
The final analysis included 257 patients, of whom the median age was 39 (IQR, 32-48) years, 84% were White, and 1 identified as a transgender woman. The majority of patients (76%) reported exclusively engaging in homosexual intercourse.
Higher concentrations of TFV-DP suggestive of daily PrEP adherence were linked to certain factors. These included older age (>50 years; P =.0008); engaging in condomless intercourse with a casual partner within the 6 months before PrEP initiation (166 fmol/punch; 95% CI, 36.5-296; P =.012); and use of a mobile app that provided visual feedback on PrEP use and sexual behavior (146 fmol/punch; 95% CI, 28.1-263; P =.015).
In contrast, lower TFV-DP concentrations suggestive of poor PrEP adherence were more likely to be observed at the 24- vs 12-month follow-up visit (-91.5 fmol/punch; 95% CI, -155 to -28.1; P =.0047). However, factors such as number of sexual partners, diagnosed sexually transmitted infections, and participating in sexual activities under the influence of substances did not have any correlation with TFV-DP concentrations.
This study was limited as the chosen outcome measure was only applicable to daily PrEP users. Although intracellular TFV-DP concentration can provide insight into mean PrEP adherence rates over time, it cannot definitively prove that PrEP was taken as needed. The researchers also noted that the analysis did not yield any clear-cut predictors of daily PrEP adherence.
“Younger PrEP users might benefit more from counseling, and an app may fulfil a facilitating role improving adherence for this digital generation,” the researchers concluded.
Disclosure: This research was supported by Gilead Sciences, and multiple authors reported affiliations with industry. Please see the original reference for a full list of disclosures.
van den Elshout MA, Hoornenborg E, Coyer L, et al; on behalf of the Amsterdam PrEP Project team in the HIV Transmission Elimination Amsterdam Initiative (H-TEAM). Determinants of adherence to daily PrEP measured as intracellular tenofovir diphosphate concentrations over 24 months of follow-up among men who have sex with men. Sex Transm Infect. 2022;0:1-8. doi:10.1136/sextrans-2022-055499