A method to detect the incidence of hepatitis C infection among injecting drug users in Glasgow 1993-98

Objectives: To determine the incidence of HCV infection in a selected population of Glasgow injectors during the mid-1990s, using a retrospective cohort design. Methods: Unlinked anonymous anti-HCV testing was undertaken on serum residues collected from injecting drug users (IDUs) having two or more voluntary named HIV tests between 1993 and 1998. Results: Seventy-seven percent (164/212) of IDUs had detectable HCV antibody in their first specimen collected. Of the 44 IDUs who were initially HCV seronegative and had a subsequent specimen available for testing, 11 (25%) seroconverted, giving an estimated incidence of 28.4 per 100 person-years (95% CI 15.7-51.2); the incidence of infection was greatest amongst older males. Conclusion: This study provides evidence of continuing transmission of HCV among Glasgow IDUs during an era of interventions to prevent the spread of bloodborne infections in this population and demonstrates the application of the unlinked anonymous testing approach to gauge incidence rather than prevalence of infection. (C) 2001 The British Infection Society.