Clinical outcomes of syphilis in HIV-negative and HIV-positive MSM: occurrence of repeat syphilis episodes and non-treponemal serology responses

Abstract

ObjectivesHIV-positive men who have sex with men (MSM) may be at a higher risk of repeat syphilis, have different clinical manifestations and have a different serological response to treatment compared with HIV-negative MSM. The objective of this study was to assess whether HIV-negative and HIV-positive MSM with infectious syphilis (primary, secondary or early latent) differed in history of previous syphilis episodes, disease stage and non-treponemal titre of initial and repeat episodes, and the titre response 6 and 12 months after treatment. Furthermore, determinants associated with an inadequate titre response after treatment were explored.MethodsThis retrospective analysis used data of five longitudinal studies (four cohorts; one randomised controlled trial) conducted at the STI clinic in Amsterdam, the Netherlands. Participants were tested for syphilis and completed questionnaires on sexual risk behaviour every 3–6 months. We included data of participants with ≥1 syphilis diagnosis in 2014–2019. Pearson’s χ² test was used to compare HIV-negative and HIV-positive MSM in occurrence of previous syphilis episodes, disease stage of initial and repeat syphilis episode and non-treponemal titre treatment responses.ResultsWe included 355 participants with total 459 syphilis episodes. HIV-positive MSM were more likely to have a history of previous syphilis episodes compared with HIV-negative MSM (68/90 (75.6%) vs 96/265 (36.2%); p<0.001). Moreover, HIV-positive MSM with repeat syphilis were less often diagnosed with primary syphilis (7/73 (9.6%) vs 36/126 (28.6%)) and more often diagnosed with secondary syphilis (16/73 (21.9%) vs 17/126 (13.5%)) and early latent syphilis (50/73 (68.5%) vs 73/126 (57.9%)) (p=0.005). While not significantly different at 12 months, HIV-negative MSM were more likely to have an adequate titre response after 6 months compared with HIV-positive MSM (138/143 (96.5%) vs 66/74 (89.2%); p=0.032).ConclusionsIn repeat syphilis, HIV infection is associated with advanced syphilis stages and with higher non-treponemal titres. HIV infection affects the serological outcome after treatment, as an adequate titre response was observed earlier in HIV-negative MSM.