Background
Sexually transmitted infections (STIs) represent a major public health challenge, particularly as many cases are asymptomatic, complicating early detection, treatment, and partner notification, and contributing to ongoing transmission. This study aims to examine the role of asymptomatic STIs in a high-risk population of men who have sex with men (MSM), who regularly undergo STI screening.
Methods
This retrospective observational study evaluated STI diagnoses between 2020 and 2023, in a cohort of at-risk individuals, specifically MSM on PrEP (MSM-PrEP) and MSM with HIV (MSMWH), with the aim of determining the rate of symptomatic and asymptomatic infections and comparing the 2 groups. Participants underwent regular screenings every 3 to 6 months, including serological tests for syphilis and molecular assays for gonorrhea and chlamydia on urethral, pharyngeal, and rectal swabs. Proportions were compared using the chi-squared test.
Results
A total of 573 participants were enrolled (458 MSMWH and 115 MSM-PrEP), resulting 1110 observed STI events (823 in MSMWH and 287 in MSM-PrEP). The frequencies of asymptomatic events in the two groups are detailed in Table 1. MSM-PrEP were more likely to have multiple STI diagnoses per person during the follow-up period compared to MSMWH (p < 0.001).
Among the STIs observed, syphilis was the most frequent, with 986 cases (819 in MSMWH and 167 in MSM-PrEP), resulting in an overall asymptomatic rate of 71.8% (708/986). Among PLWH, 543/819 cases (66.3%) were asymptomatic, compared to 165/167 cases (98.8%) in the MSM-PrEP, with a statistically significant difference (p <0.001).
We identified 75 cases of gonorrhea (12 in MSMWH and 63 in MSM-PrEP), with an overall asymptomatic rate of 49.3% (37/75). For chlamydia, there were 50 cases (10 in MSMWH and 40 in MSM-PrEP), with 44.0% asymptomatic (22/50). There were no statistically significant differences in the clinical presentation of these two STIs between the two groups.
Conclusions
Asymptomatic STIs are notably common in this population, with a significant frequence of syphilis observed. A significant difference in the rate of asymptomatic cases was found specifically for syphilis between the two groups. MSM-PrEP had a higher frequency of multiple STI diagnoses per person during the follow-up period compared to MSMWH. These findings emphasize the need for effective prevention strategies to manage STIs in these populations and highlight the importance of regular screening to ensure timely detection and treatment.