Introduction Infection with the hepatitis C virus (HCV) is associated with the development of severe liver disease, but cofactors – namely alcohol abuse – in Scotlands HCV-positive population complicate estimation of the unique contribution of HCV. We compared the risk of hospital admission/death for a liver-related cause in a large cohort of Glasgow's injecting drug users (IDUs) testing HCV-positive, with IDUs testing HCV-negative.

Methods Data for 6566 current/former IDUs who had been tested for anti-HCV and/or HCV RNA in Greater Glasgow health board between 1993 and 2007 were linked to the national hospitalisation database and deaths registry to identify all admissions and deaths from a liver-related condition. RRs were estimated using Cox regression for recurrent events.

Results The risk of hospitalisation/death from a liver-related or an alcoholic liver-related condition following HCV testing was greater for those IDUs with no prior alcohol-related hospitalisation who tested positive [adjusted hazard ratio (HR) = 3.2, 95% CI 1.5 to 6.7; 4.9, 95% CI 1.8 to 13.1, respectively], compared with those who tested anti-HCV negative, but not for those IDUs with a prior alcohol admission (HR=0.8, 95% CI 0.4 to 1.5; 0.8, 95% CI 0.4 to 1.6). There was little evidence for an increased risk of hospitalisation/death for an exclusively non-alcoholic liver condition for those testing positive (HR=1.5, 95% CI 0.8 to 2.7), after adjustment for previous alcohol-related admission.

Conclusion Within Glasgow's IDU population, HCV positivity is associated with an increased risk of a liver-related outcome, but this is not observed for those IDUs whose problem alcohol use already increases their risk.