Impact of Hepatitis C treatment on behavioural change in relation to drug use in people who inject drugs: A systematic review

Background: A systematic review was conducted to determine the impact of Hepatitis C (HCV) treatment on substance use behaviour in people who inject drugs (PWID). Methods: A search for peer reviewed journal articles from 1991 to present day was conducted using the following databases: PubMed, EMBASE, CINAHL and PsycINFO. Studies were appraised against the following inclusion criteria: recruitment of PWID for HCV treatment (either interferon alpha or direct acting antivirals based); measurement of behavioural change in relation to drug use; studies published in English. Results: Five studies investigating the impact of HCV treatment on behavioural change in relation to drug use amongst PWID were identified. Studies investigated the impact of HCV treatment on past month injecting drug use (four studies), injecting frequency (two studies), needle and syringe borrowing (two studies) and injecting equipment sharing (three studies). Three of the four studies assessing impact of treatment on past month injecting frequency found treatment significantly reduced the odds of participants reporting past month injecting at follow up. One study found that there was significant reduction in weekly injecting frequency between enrolment, treatment and follow up. No association was found between treatment engagement and needle and syringe borrowing. Two out of three studies reported a significant decrease in injecting equipment sharing between enrolment, treatment and follow up. Conclusions: Comparison and synthesis of results was challenging due to heterogeneity between studies. Moreover, four out of the five selected studies were conducted during the interferon era of treatment, possibly limiting the generalisability of the current review's results to the new DAA treatment era. However, it is likely that engaging in treatment has a positive impact upon patients' injecting drug use and injection equipment sharing behaviour. This raises the possibility that this may be an opportune time for further harm reduction measures.