Impact of Pre-exposure Prophylaxis (PrEP) on sexually transmitted infection (STI) incidence among men who have sex with men (MSM) in Mecklenburg County North Carolina Open Access

Omerhi, Isaiah (Fall 2019)

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Objective: This study aims to determine whether MSM who were prescribed Truvada pre-exposure prophylaxis (PrEP) have a higher incidence of sexually transmitted infections (STIs) than MSM not using Truvada PrEP.

Design: Primary analysis of longitudinal STI data obtained from MSM attending Rosedale Medical and Amity Medical Group in Charlotte North Carolina, USA, and January 2016–October 2018.

Methods: Men who have sex with men (MSM) patients were identified and grouped into two, those who were prescribed Truvada PrEP and a second group not using PrEP (propensity score was used to match similar patients). Patients' STI data was used to compare the incidence of chlamydia, gonorrhea, and syphilis, and time to first symptomatic STI among PrEP users and nonusers.

Results: Ninety-eight Truvada PrEP users propensity score matched nonusers were included in the analysis. Incidence rate ratios (IRRs) for chlamydia, gonorrhea and early syphilis were 3.2 [95% confidence interval (95% CI): 1.9–5.3], 2.8 (95% CI: 1.7–4.6) and2.9 (95%CI: 1.5 – 5.6), respectively, comparing PrEP users to nonusers. Time to first symptomatic STI was shorter among PrEP users (120 days, 95% CI: 77 – 171) than among nonusers (185 days, 95% CI: 163–256).

Conclusion: Among MSM on Truvada PrEP, we observed a higher incidence of STIs and faster time to first symptomatic STI than MSM, not on Truvada PrEP. Truvada PrEP nonusers had a higher incidence of syphilis compared to Truvada PrEP users. However, there is insufficient evidence that PrEP maybe a contributing factor in increasing STI rates among MSM.

Table of Contents

Background. 1

Method. 5

Propensity Score Matching and Comparison Group Formation. 6

Data Sources, Measures and Data Linkage. 7

Sexually Transmitted Infection Testing. 7

Statistical Analysis and Follow-up Time Calculation. 7

Results. 8

Figure 1: Patients included in analysis. 8

Table 2: Incidence of STIs among PrEP users and nonusers attending Rosedale Medical and Amity Medical Group – Mecklenburg County (2016–2018), N=196. 10

Table 3: Time to STI among Truvada PrEP users and nonusers in Rosedale Medical and Amity Medical Group in Mecklenburg County North Carolina (2016-2018), N= 196. 11

Discussion. 11

Figure 2: Kaplan-Meier of STI incidence between Truvada PrEP users and nonusers. 12

Figure 3: Log-Negative Log of Estimated Survivor Functions of STI incedence among PrEP users and nonusers. 15

Limitations. 16

Conclusion. 17

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