Prevalence study on the use of substances in relation with hepatitis (PUSH) in Brussels

Introduction: Existing data about the number of people who inject drugs (PWID) and about the number of high-risk opioid users (HROU) in Belgium are considered unreliable. Also hepatitis C (HCV) prevalence figures for people who use drugs, and more specifically among PWID and HROU, are rare and outdated. The PUSH-study is a pilot project to test a methodology for the prevalence estimation of PWID, HROU and HCV among PWID and HROU in Brussels, in preparation of a study on a national level. As injecting drug use is the most common mode of transmission of hepatitis C in Belgium, results will be important for prevention, treatment and harm-reduction initiatives.

Methods: For the estimation of HCV among PWID and HROU respondent driven sampling (RDS) will be used. Respondents will undergo a rapid anti-HCV test and answer a short questionnaire to allow a better understanding of the link between HCV and possible risk factors. RDS fieldwork will take place in Brussels between February and April 2019. For the prevalence study on PWID and HROU in Brussels, the capture/recapture method (CRC) will be applied to three data sources: treatment facilities, needle exchange services and the data collected through RDS.

Results: Log-linear modelling will be used to estimate the total population size of PWID and HROU in Brussels. RDS Analysis Package ‘RDS’ for R will be used to estimate the number of people with HCV among them.

Conclusion: Firstly, the estimates of PWID, HROU and HCV will be discussed and related to previous estimations in Belgium and abroad. Secondly, the use of CRC and RDS will be discussed as methods for prevalence studies among hard-to-reach population. Finally, emphasis will be on the feasibility and challenges for the study on a national scale.