Representativeness of participants in a randomized controlled trial on modalities of monitoring oral HIV pre-exposure prophylaxis use

BACKGROUND: We assessed whether participants in the EZI-PrEP study, a non-inferiority trial evaluating online and six-monthly monitoring of oral HIV pre-exposure prophylaxis (PrEP), represent the broader population of PrEP users in the Netherlands. METHODS: We conducted a cross-sectional study using routinely collected data from September 2021 to August 2022 at four centres for sexual health (CSHs) in the Netherlands. Socio-demographic characteristics, sexual behaviour, and prevalence of bacterial STIs were compared between EZI-PrEP participants at baseline and other PrEP users during their first PrEP monitoring visit during the same period. RESULTS: The analysis included 469 EZI-PrEP participants and 5161 other PrEP users, of whom 99% and 96% were men who have sex with men (MSM), respectively. EZI-PrEP participants were less often transgender or gender-divers persons (TGDP) (1% vs. 4%, p < 0.001), older (median age = 36 vs. 34 years, p = 0.004), more often born in the Netherlands (68% vs. 58%, p < 0.001), and more often completed a university/college degree (81% vs. 76%, p = 0.01). They also reported more group sex (38% vs. 33%, p = 0.023) and condomless anal sex (95% vs. 92%, p = 0.004), but less often sex work (1% vs. 6%, p < 0.001). Prevalence of bacterial STIs were no different between groups (19% vs. 18%, p = 0.77). CONCLUSIONS: The comparable STI prevalence suggests no difference in risk for HIV acquisition among EZI-PrEP participants and other PrEP users, making study outcomes applicable to a broader population of PrEP users. However, under-representation of TGDPs, sex workers, individuals not born in the Netherlands, and individuals without university or college degree may limit generalizability.