Impact of reduced-frequency monitoring among users of HIV pre-exposure prophylaxis on sexually transmitted infections and associated care secondary outcomes of a randomized controlled trial

Background Oral HIV pre-exposure prophylaxis (PrEP) users are generally screened for sexually transmitted infections (STIs) every 3 months. The need for such frequent screening is debatable. We compared STI diagnoses and associated care between PrEP users who underwent 6-monthly versus 3-monthly PrEP monitoring.
Methods  We conducted a secondary analysis of the EZI-PrEP study- a 2 × 2 factorial randomized controlled trial examining 6-monthly versus 3-monthly and online versus in-clinic PrEP monitoring among men who have sex with men (MSM) and transgender or gender-diverse persons in the Netherlands (2021-2024). Participants were followed for 24 months. Scheduled PrEP monitoring included bacterial STI screening (i.e., Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT), syphilis). Unscheduled STI testing in-between monitoring visits was permitted. This secondary analysis compared several outcomes between the 6-monthly and 3-monthly monitoring groups, using Poisson regression: (i) visit rates as number of visits per person-year (PY), (ii) STI detection rates as number of STI diagnoses per 100PY (to assess STI detection and potential (over)treatment), and (iii) STI positivity as number of STI diagnoses per 100 visits (as proxy for diagnostic delay). We stratified outcomes by visit type (i.e., scheduled/unscheduled) and adjusted for sexual behavior.
Results  451 participants (99% MSM) were followed for median 22.7 months (IQR 19.2-23.8). Compared to 3-monthly PrEP monitoring, 6-monthly monitoring led to 31% fewer visits in total (rate ratio = 0.69, 95%CI = 0.64-0.74), but 67% more unscheduled visits (rate ratio = 1.67, 95%CI = 1.42-1.98). The STI detection rate was 18% lower in the 6-monthly monitoring group (adjusted rate ratio = 0.82, 95%CI = 0.70-0.95). STI positivity at PrEP monitoring visits did not differ between monitoring groups (6-monthly: 23.8 STIs/100 visits; 3-monthly: 23.2 STIs/100 visits; adjusted positivity ratio = 1.09, 95%CI = 0.90-1.30).
Conclusions  Reduced-frequency PrEP monitoring resulted in fewer total clinic visits, but more self-initiated STI testing. Furthermore, fewer STIs were diagnosed during follow-up, yet the number of STIs detected per scheduled monitoring visit was similar between groups. These findings suggest that less frequent PrEP monitoring could reduce the burden of PrEP care and the number of STIs that are detected and treated, without leading to a substantial rise in STIs.TRIAL REGISTRATION: The trial has been registered with ClinicalTrials.gov, trial number NCT05093036 (https://clinicaltrials.gov/study/NCT05093036).