Background Hepatitis C (HCV) among HIV positive men who have sex with men (MSM) who deny injection drug use is likely to be acquired through sexual contact. Recurrent Sexually Transmitted Infections (STIs) are an indication of unsafe sexual practices and may be associated with HCV infection.

Methods In a retrospective study we analysed the laboratory data of 16 HCV positive/HIV positive MSM (cases), HCV diagnosis in 2010, and 32 HCV negative/HIV positive MSM (controls), followed at the HIV/STI clinic in Antwerp, Belgium. All laboratory confirmed STI episodes (syphilis, gonorrhoea, lymphogranuloma venereum, and rectal and urethral non-LGV chlamydial infections) were recorded since the date of presentation at our clinic, until the date of HCV diagnosis of the cases. Controls were selected from consecutive patients that consulted on the same day. Both cases and controls were regularly followed up at the clinic in view of their HIV infection. Syphilis screening is part of the three or four monthly laboratory check-up. The clinic is the first point of contact in case of signs or symptoms of an STI. STI episodes were defined on the basis of laboratory results—HCV infection was determined using a screening test and confirmed with a Line Immunoassay. Syphilis was diagnosed by RPR and TPPA seroconversion (primo-infection) or ≥ fourfold rise of RPR-titre (re-infection), gonorrhoea by culture and chlamydial infection by PCR. All STI episodes were treated according to CDC treatment guidelines 2010. We applied Poisson regression to assess the difference in STI-episodes per person-month of follow-up between cases and controls.

Results During 1049 and 1848 months of follow-up of the cases and controls respectively, 57 periods of STIs were diagnosed—32 periods of syphilis, 12 periods of gonorrhoea, 4 periods of lymphogranuloma venereum, 9 periods of rectal or urethral non-LGV Chlamydia trachomatis. The number of STI episodes per person-month follow-up was significantly higher for the cases as compared to the controls (p=0.005) see Abstract P1-S2.56 Table 1.

Conclusion The number of episodes of Sexually Transmitted Infections, prior to acquisition of HCV was significantly higher for HCV positive cases than for HCV negative controls. All patients were followed at the clinic for HIV positivity, as such an indication of risky sexual behaviour. The higher number of STIs in the history of the HCV cases may be associated with acquiring HCV. Cases and controls are enrolled in a larger study involving an in depth structured questionnaire that should shed light on behavioural factors that are associated with HCV infection. In Antwerp, a setting with a rising incidence of HCV among HIV positive MSM, an easy to recognise event such as recurrent STIs should lead to intensified screening for HCV and counselling of the patient.