Needle and syringe programmes and opioid substitution therapy for preventing HCV transmission among people who inject drugs: findings from a Cochrane Review and meta-analysis

AIMS: To estimate the effects of needle syringe programmes (NSP) and opioid substitution therapy (OST), alone or in combination, for preventing acquisition of Hepatitis C virus (HCV) in people who inject drugs (PWID). METHODS: Systematic review and meta-analysis. Bibliographic databases were searched for studies measuring concurrent exposure to current OST (within last 6 months) and/or NSP and HCV incidence among PWID. High NSP coverage was defined as regular NSP attendance or ≥100% coverage (receiving sufficient or greater number of needles/syringes per reported injecting frequency). Studies were assessed using the Cochrane risk of bias in non-randomised studies tool. Random effects models were used in meta-analysis. RESULTS: We identified 28 studies (n=6279) in North America (13), UK (5), Europe (4), Australia (5), and China (1). Studies were at moderate (2), serious (17) critical (7) and non-assessable risk of bias (2). Current OST is associated with 50% (risk ratio (RR) 0.50 95% CI 0.40-0.63) reduction in HCV acquisition risk, consistent across region and with low heterogeneity (I(2) =0, p=0.889). Weaker evidence was found for high NSP coverage (RR=0.79 95% CI 0.39-1.61) with high heterogeneity (I(2) =77%, p=0.002). After stratifying by region, high NSP coverage in Europe was associated with a 56% reduction in HCV acquisition risk (RR=0.44, 95% CI 0.24-0.80) with low heterogeneity (I(2) =12.3%, p=0.337) but not in North America (RR=1.58, I(2) =89.5%, p=