Research ArticleArticles

Self-Reported PrEP Use and Risk of Bacterial STIs Among Ontarian Men Who Are Gay or Bisexual or Have Sex With Men

Nguyen K. Tran, Seth L. Welles, Jason A. Roy, David J. Brennan, Esther Chernak and Neal D. Goldstein
The Annals of Family Medicine August 2024, 3152; DOI: https://doi.org/10.1370/afm.3152

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  • SUPPLEMENTAL APPENDIX, FIGURES, AND TABLES IN PDF FILE BELOW

    • Tran_Supplemental.pdf -

      Supplemental Appendix. Inverse probability of exposure and attrition weights; Quantitative bias analysis for outcome nondifferential misclassification

      Supplemental Figure 1. Directed acyclic graph for the association of pre-exposure prophylaxis uptake and bacterial sexually transmitted infections (STI) over follow-up in the Diary arm of the iCruise Study, Ontario, Canada, 2017-2018. 

      Supplemental Figure 2. Distribution of nonstabilized and stabilized weights for exposure by pre-exposure prophylaxis uptake over follow-up. The box for each group shows the median (middle horizontal bar) as well as the first and third quartiles (border horizontal bars). Vertical lines extend to observations that are 1.5 × interquartile range.

      Supplemental Figure 3. Distribution of unstabilized and stabilized weights (exposure weights × lost to follow-up weights) summed across all follow-up visits by pre-exposure prophylaxis uptake. The box for each group shows the median (middle horizontal bar) as well as the first and third quartiles (border horizontal bars). Vertical lines extend to observations that are 1.5 × interquartile range. 

      Supplemental Figure 4. Lagged association of PrEP uptake and incidence rate ratio (95% confidence interval) of any bacterial sexually transmitted infections, chlamydia, gonorrhea, and syphilis.

      Supplemental Table 1. Characteristics of gay, bisexual, and other men who have sex with men by study completion in the Diary arm of the iCruise study, Ontario, Canada, 2017-2018 

      Supplemental Table 2. Characteristics of the study population for the LA LGBT Center and iCruise study 

      Supplemental Table 3. Summary of parameters from external literature for quantitative bias analysis of nondifferential outcome misclassification


  • PLAIN LANGUAGE SUMMARY OF ARTICLE

    Original Research 

    Higher Gonorrhea Rates Observed Among Gay and Bisexual Men in Ontario Using PrEP Compared With Non-Users

    Background and Goal: Pre-exposure prophylaxis (PrEP) is a preventive medicine that reduces the risk of contracting HIV. While there is concern that PrEP use may be associated with an increase in bacterial sexually transmitted infections (STIs) like gonorrhea, chlamydia, and syphilis among gay, bisexual, and other men who have sex with men, the reasons for this association are complex. This study aimed to explore the relationship between PrEP use and the rates of bacterial sexually transmitted infections over time.

    Study Approach:  Researchers used data from the iCruise Study, an online longitudinal study of gay, bisexual, and men who have sex with men in Ontario from July 2017 to April 2018, to examine how PrEP use related to the number of self-reported bacterial STIs. For this study, 659 participants in the iCruise Study were randomly selected to participate in a weekly diary survey for up to a three-month study period. Instances of chlamydia, gonorrhea, and syphilis infections were measured as the number of infections per 100 months of participant observation time. The overall infection rate and each type of infection were evaluated separately.

    Main Results:

    • 535 participants in the iCruise Study were included in the analysis. Participants were followed for a total of 1623.5 person-months (the total time all participants were in the study). About 13.1% (70 participants) reported using PrEP during the study period.

    • PrEP use was linked to a higher rate of gonorrhea:

    • The initial analysis suggested that the rate of gonorrhea among PrEP users was four times higher than among non-users, with an incidence rate ration of 4.00 (95% CI, 1.67-9.58)

    • After conducting a bias analysis to account for potential inaccuracies in self-reported data, the association remained, though it was somewhat less pronounced. The adjusted analysis showed that PrEP users were still at a higher risk, with a median incidence rate ration of 2.36 (simulation interval: 1.08-5.06)

  • There was no significant increase in the rates of chlamydia or syphillis among PrEP users

    • Why It Matters: Individuals who choose to take PrEP are at higher risk for gonorrhea and should be regularly tested and treated to manage this risk effectively. The findings of this study highlight the importance of investing in sexually transmitted infection testing, risk reduction, secondary prevention measures such as Doxycycline Post-Exposure Prophylaxis (a preventive treatment to reduce the risk of bacterial STIs after potential exposure), surveillance, and partner management alongside PrEP to reduce bacterial STI transmission effectively.  This approach is necessary regardless of whether the increased risk is due to pre-existing factors or potential behavior changes associated with PrEP use. 

    Self-Reported PrEP Use and Risk of Bacterial STIs Among Ontarian Men Who Are Gay or Bisexual or Have Sex With Men

    Nguyen K. Tran, PhD, MPH, et al 

    Stanford University School of Medicine, Palo Alto, CA, USA

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