The impact of methadone maintenance therapy on hepatitis C incidence among illicit drug users

AimsTo determine the relationship between methadone maintenance therapy (MMT) and hepatitis C (HCV) seroconversion among illicit drug users. DesignA generalized estimating equation model assuming a binomial distribution and a logit-link function was used to examine for a possible protective effect of MMT use on HCV incidence. SettingData from three prospective cohort studies of illicit drug users in Vancouver, Canada between 1996 and 2012. ParticipantsA total of 1004 HCV antibody-negative illicit drug users stratified by exposure to MMT. MeasurementsBaseline and semi-annual HCV antibody testing and standardized interviewer-administered questionnaire soliciting self-reported data relating to drug use patterns, risk behaviors, detailed socio-demographic data and status of active participation in an MMT program. FindingsOne hundred and eighty-four HCV seroconversions were observed for an HCV incidence density of 6.32 [95% confidence interval (CI)=5.44-7.31] per 100 person-years. After adjusting for potential confounders, MMT exposure was protective against HCV seroconversion [adjusted odds ratio (AOR)=0.47; 95% CI=0.29-0.76]. In subanalyses, a dose-response protective effect of increasing MMT exposure on HCV incidence (AOR=0.87; 95% CI=0.78-0.97) per increasing 6-month period exposed to MMT was observed. ConclusionParticipation in methadone maintenance treatment appears to be highly protective against hepatitis C incidence among illicit drug users. There appears to be a dose-response protective effect of increasing methadone exposure on hepatitis C incidence.