Syphilis presentation among PrEP users and non-users: A comparative study

Introduction In 2023, 10,879 cases of syphilis were diagnosed in Spain, with an annual increase of 24.1% between 2021 and 2023. The PrEP programme was implemented in 2019, providing regular screening for STIs, including syphilis, to enable early diagnosis during the asymptomatic phase. This study aims to evaluate the association between PrEP use and the presentation of syphilis at an STI clinic in Barcelona. Methods This was a single-centre, retrospective, comparative study of patients diagnosed with early syphilis in 2023. Demographic, behavioural, and clinical variables were collected and compared between individuals using PrEP and those not using it. Results A total of 290 cases of early syphilis were diagnosed in 2023: 52 (17.9%) primary syphilis, 88 (30.3%) secondary syphilis, and 150 (51.7%) early latent syphilis. Of these, 157 (54.1%) were on PrEP; among the 133 not on PrEP, 51 (38%) were HIV-positive. Of those on PrEP, 111 (70.7%) were diagnosed at the time of their follow-up visit, of whom 34 (30%) were symptomatic. Comparison of clinical presentation showed that early latent syphilis was more frequent in the PrEP group (60% vs 42%, p < 0.001). There were no significant differences in most behavioural variables, except for number of sexual contacts. Conclusions Early latent syphilis was diagnosed more frequently in individuals on PrEP than in those not using PrEP, likely due to the regular screening provided within the programme.