Incidence and Risk Factors for Hepatitis C Seroconversion in Injecting Drug Users in Australia

The authors conducted a prospective cohort study to determine the incidence of hepatitis C virus (HCV) infection and to identify risks for seroconversion. Study participants were recruited through direct approach, street-based outreach, methadone and sexual health clinics and needle/syringe programs in New South Wales.

The researchers identified 584 injecting drug users (IDUs) and screened and tested them for HCV exposure. Between 1999 and 2002, 368 HCV-negative IDUs were enrolled. Follow-up was conducted every 3-6 months until seroconversion or the end of the study. At baseline and follow-up, interviewers administered questionnaires with 131 items detailing demographics, drug use and risk behavior. At each visit, 10cc of whole blood was drawn. The specimens were stored at -70C, and serology was performed using one or two third-generation enzyme-linked immunosorbent assays and polymerase chain reaction testing.

During the study, 68 seroconversions were documented. Incidence was 30.8 per 100 person-years, with incidence in IDUs injecting less than one year 133 per 100 person-years. Female gender, duration of injecting, injecting cocaine, sharing filters, and recruitment strategy were independent predictors of seroconversion.

"Women, new initiates, and IDUs recruited via outreach appear to be at increased risk of infection," the researchers concluded. "Results confirm the significance of cocaine injection as a risk factor and provide the first evidence outside North America of the link between shared use of drug preparation equipment and incident HCV infection. Prevention efforts should attempt to raise awareness of the risks associated with drug sharing and, in particular, the role of potentially contaminated syringes in HCV infection."

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