Review and meta-analysis of the association between self-reported sharing of needles/syringes and hepatitis C virus prevalence and incidence among people who inject drugs in Europe

BackgroundAlthough sharing needles/syringes (N/S) is a recognised risk factor for the hepatitis C virus (HCV), epidemiological studies have shown inconsistent associations between self-reported N/S sharing and biological markers of HCV infection. This review aims to summarise, and explore factors that may explain the variation in, the measure of association between self-reported sharing of N/S and HCV prevalence/incidence among people who inject drugs (PWID).MethodsStudies undertaken in Europe during 1990–2011 were identified through an electronic literature search. Eligible studies reported HCV prevalence (or incidence) among those who reported ever/never (or recent/non-recent) sharing of N/S. Meta-analysis was undertaken to generate a pooled estimate of the association and heterogeneity was explored using stratified analyses.ResultsSixteen cross-sectional studies and four longitudinal studies were included. Pooled prevalence and incidence of HCV was 59% and 11% among PWID who reported never and not recently sharing N/S, respectively. Random effects meta-analysis generated a pooled odds ratio (OR) of 3.3 (95% CI 2.4–4.6), comparing HCV infection among those who ever (or recently) shared N/S relative to those who reported never (or not recently) sharing. There was substantial heterogeneity between the study effect sizes (I2 = 72.8%). Differences in pooled ORs were found when studies were stratified by recruitment setting (prison vs. drug treatment sites), recruitment method (outreach vs. non-outreach), sample HCV prevalence and sample mean/median time since onset of injecting.ConclusionWe found high incidence/prevalence rates among those who did not report sharing N/S during the risk period, which may be due to a combination of unmeasured risk factors and reporting bias. Study design and population are likely to be important modifiers of the size and strength of association between HCV and N/S sharing.