This study measures the prevalence of undiagnosed hepatitis C virus (HCV) infection in HIV-negative men-who-have-sex-with-men (MSM) visiting the sexual health clinics of public health services (in dutch: gemeentelijke gezondheidsdienst, GGD), in order to evaluate if systematic screening for HCV of HIV-negative MSM attending sexual health clinics in the Netherlands is needed.

Until recently, sexually acquired HCV infections were thought to be limited to HIV-positive MSM. Yet, emerging data show that the prevalence of HCV among HIV uninfected MSM that opt-in for HIV pre-exposure prophylaxis (PrEP) is much higher. It was 5% (n=18/375) in Amsterdam and 2% (n=4/200) in Antwerp (Be-PrEP-ared; EudraCT2015-000054-37) (23).

This observation may be the result of the fact that PrEP users are, by definition, at risk for sexually transmitted infections because PrEP is only prescribed to those at risk for HIV. However, another explanation may be that in the new context of HIV "treatment as prevention" and the availability of PREP as a way to protect oneself against HIV, the incidence of HCV in HIV uninfected MSM is changing. Furthermore, if PrEP use would lead to an increase in sexual risk-taking, this may eventually lead to an increase in the incidence of HCV among HIV negative MSM on PrEP. If these HCV infections among HIV negative MSM remain unnoticed, they are a continuous source of HCV infections in HIV+MSM as well for the larger HIV-MSM community. Furthermore, PrEP as well as the very well-documented efficacy of HIV treatment as prevention can be expected to increase sexual mixing of HIV- and HIV+MSM.

Based on the observations described above, we hypothesize that undiagnosed HCV infections in HIV negative MSM are (or may become) an important source of HCV (re)infections in HIV+MSM as well as the larger HIV-MSM population.

Primary objectives:

1. Measure the prevalence of HCV in a large group of HIV-negative MSM attending sexual health clinics in the Netherlands.
2. Assess Risk Factors for HCV in order to validate the HCV-MOSAIC risk score in HIV-MSM, which may allow for a more cost-effective (=targeted) HCV testing of HIV-MSM in the future

Secondary objectives:

1. Measure the acceptability of HCV testing in HIV-MSM at public health clinics.
2. Evaluate the HCV outcome in terms of the proportion of HCV infections that cleared spontaneously (= HCV IgG positive but HCV RNA negative) versus the total number of HCV IgG positive clients.

The HCV-immunoglobulin G (IgG) test is offered on top of the regular sexually transmitted infection (STI) tests. A positive HCV-IgG test will be followed by an HCV-RNA test. Clients known to be HCV IgG positive as a result of a previous HCV infection will be tested for HCV using an HCV-RNA test.

Before HCV testing, participants will be asked to fill out a detailed study questionnaire about possible risk factors for HCV acquisition (PREP use, receptive unprotected anal intercourse, use of non-IV or injection drugs during sex, fisting, recent diagnosis of ulcerative rectal STI, etc.).

Inclusion Criteria:

• Self-identifying as a man-who-has-sex-with-men (MSM)
• Willing to undergo HCV testing

Exclusion Criteria:

• Clients known to be HIV positive