P1-44 Application of a novel method to estimate incidence of hepatitis C among injecting drug users in Scotland

BackgroundPrevalence of the hepatitis C virus (HCV) among injecting drug users (IDUs) in Scotland is high. Through an HCV Action Plan, the Scottish Government has invested significantly in harm reduction interventions with the goal of reducing HCV transmission among IDUs. In evaluating the effectiveness of interventions, estimates of the incidence, rather than the prevalence, of HCV are essential. The traditional approach to measuring incidence—follow-up of a cohort of uninfected individuals to measure seroconversion—can, however, be costly and suffer high participant attrition rates. We report the first large-scale, national application of a novel method designed to determine incidence of HCV using a cross-sectional design.MethodsDuring 2008–2009, IDUs were recruited from needle exchange services, completed an interviewer-administered questionnaire and provided a dried blood spot for anonymous HCV-antibody (anti-HCV) and HCV-RNA testing. Incident infections were defined as individuals who were anti-HCV negative and HCV-RNA positive.ResultsPrevalence of anti-HCV was 55% among the 2563 participants. Among anti-HCV negative respondents, twenty-one were HCV-RNA positive, yielding an incidence estimate of 12.1 per 100 person-years (corresponding to a viraemic pre-seroconversion window period of 51 days). Individuals currently receiving methadone had lower odds of incident infection (adjusted OR 0.15; 95% CI 0.035 to 0.68) relative to those on methadone in the previous 6 months (but not currently).ConclusionsThis approach to measuring incidence will allow us to gauge the impact of preventive interventions associated with the HCV Action Plan.