# Retrospective analysis of sexually transmitted infections among people living with HIV and pre-exposure prophylaxis users in Spain

## TL;DR

This study compared STI rates in people with HIV and those on PrEP in Spain, finding higher STI rates in PrEP users but no significant difference after adjusting for factors like chemsex use.

## Contribution

The study provides new insights into STI profiles and risk factors among HIV-positive individuals and PrEP users in Spain.

## Key findings

- PrEP users had a higher STI prevalence (38.2%) compared to PWH (28.2%), but the difference was not significant after adjustment.
- Chemsex use and higher education were independently associated with STI diagnosis.
- Different bacterial STI profiles were observed between PWH and PrEP users.

## Abstract

This study aimed to compare the frequency and characteristics of sexually transmitted infections (STI) between people with HIV (PWH) and pre-exposure prophylaxis (PrEP) users.

A retrospective analysis was conducted using nucleic acid amplification techniques (NAAT) for Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma genitalium in rectal, urine, and pharyngeal samples, as well as serological tests for syphilis. The samples were collected and analysed as part of routine clinical care and sent to the microbiology department between Jan 1 2023, and May 31 2023. Multivariable logistic regression was performed to identify factors associated with STI diagnosis; adjusted odds ratios (aOR) and 95% confidence intervals (CI) were reported.

A total of 459 samples from 450 participants (277 PWH and 173 on PrEP) were included in the analysis. Overall, 144 (32%) participants tested positive for at least one STI. PrEP users had a lower median age (35 vs. 42 years; p < 0.01), were more frequently born in Spain (77.5% vs. 57.6%; p < 0.01), had a higher level of education (university 62.4% vs. 48.4%; p < 0.01), and had a higher prevalence of chemsex use (18.4% vs. 12.9%; p < 0.01). The prevalence of STIs was significantly higher among the PrEP users (38.2% vs. 28.2%; p = 0.027). However, this difference was insignificant after multivariable adjustment (aOR 1.09, 95% CI 0.6–1.7). Neisseria gonorrhoeae was the most common pathogen among PrEP users, while Chlamydia trachomatis and Mycoplasma genitalium were more frequent in PWH. Independent factors associated with STI diagnosis included chemsex use (aOR 1.9, 95% CI 1.1–3.3) and higher educational level (aOR 2.4, 95% CI 1.7–3.4).

STIs were commonly diagnosed among PWH and PrEP users, particularly in individuals engaging in chemsex. The different bacterial profiles of STI between PWH and PrEP users underline the importance of continuous STI surveillance.

Not applicable.

The online version contains supplementary material available at 10.1186/s12879-025-12395-z.