STI Testing Every Six Months May Be Enough for PrEP Users

Men on HIV pre-exposure prophylaxis (PrEP) who were tested for sexually transmitted infections (STIs) every six months instead of every three months accrued fewer total visits without raising the likelihood of testing positive for STIs, according to study results presented at the International AIDS Conference (#AIDS2024).

“We think we can argue that six-monthly PrEP monitoring would reduce health care costs and be less burdensome for the PrEP user without major increases in STI positivity,” lead investigator Marije Groot Bruinderink, of the Amsterdam Public Health Service, told reporters at a conference news briefing.

Until recently, quarterly PrEP monitoring—which includes testing for chlamydia, gonorrhea and syphilis—was the standard of care in the Netherlands. Likewise, the U.S. Centers for Disease Control and Prevention PrEP guidelines recommend screening for bacterial STIs at least once every three months for gay and bisexual men and transgender women and once every six months for other sexually active individuals.

The EZI-PrEP study was designed to both assess less frequent PrEP monitoring and to compare in-person versus online monitoring. Participants are randomly assigned to receive PrEP monitoring every three months in a clinic, every three months online, every six months in a clinic or every six months online. In addition, they could come in for free STI testing in between scheduled visits—for example, if they developed symptoms.

The main study outcome is PrEP adherence; those results are expected later this year. The preliminary analysis presented at AIDS 2024 focused on the number of clinic visits and STI positivity rates in the every-three-months versus every-six-months groups.

This analysis included 448 men who have sex with men and five trans women or gender-diverse people at four study sites in Amsterdam, Rotterdam, the Hague and Nijmegen. The median age was 36 years, 68% were born in the Netherlands and 79% had the equivalent of a university education. The participants were enrolled between September 2021 and July 2022 and followed through March 2024.

People who were monitored every six months had more in-between clinic visits compared with the every-three-months group (274 versus 157, respectively), but their total number of visits was still lower (862 versus 1,288, respectively), Bruinderink reported.

There was no significant difference in overall STI positivity rates in the two groups. Looking at all visits, there were 29.1 STI cases per 100 visits in the every-six-months group compared with 25.6 in the every-three-months group. Rates were higher in both groups—but again not significantly different—when considering only in-between visits (41.2 versus 45.2 cases per 100 visits, respectively). People in the every-six-months group were slightly more likely to test positive for asymptomatic STIs (27.0 versus 22.5 cases per 100 visits, respectively), however.

PrEP monitoring every six months versus every three months led to more in-between STI test visits, fewer scheduled monitoring visits, fewer overall visits and similar overall STI positivity rates, the researchers concluded.

A three-month delay in diagnosing asymptomatic STIs does not appear to affect treatment or outcomes, and there is “no proven effect of frequent STI screening on STI prevalence in dense sexual networks,” Bruinderink noted.

Dutch PrEP guidelines were recently changed to recommend monitoring every six months as the standard of care in 2024. “If we see people two times a year instead of four times a year, we can increase the number of people in our PrEP program” for the same budget, she added. Longer intervals between visits could be even more helpful in regions with inadequate health funding or staffing or where transportation is a challenge.

“The findings suggest that implementing PrEP monitoring every six months as standard care could bring down the number of visits without increasing STIs,” AIDS 2024 cochair Christopher Spinner, of the Technical University of Munich, said at the briefing. “That could, of course, reduce costs and, more importantly, reduce a key barrier to PrEP uptake and adherence.”