Initiating HCV treatment with direct acting agents in opioid agonist treatment: When to start for people co-infected with HIV?

Background: Direct acting antivirals (DAA) raise the possibility of eliminating Hepatitis C virus (HCV) among people who inject drugs (PWID). However, concerns regarding treatment retention and reinfection challenge implementation efforts. Opioid agonist treatment (OAT) provides an opportunity to engage HCV-positive PWID into DAA-based treatment. Our objective was to identify when OAT adherence sufficiently improved to inform DAA initiation in OAT settings, assuming continuous OAT retention for at least twelve weeks is necessary to complete the DAA treatment course.
Methods: This was a retrospective cohort study of HCV/HIV co-infected PWID from a population-level linked administrative database of people diagnosed and living with HIV in British Columbia, Canada between 01/1996 and 12/2013. We used monthly follow-up data after initial OAT entry and considered the effects of demographics, disease severity, and HIV and OAT treatment characteristics over time on the probability of subsequent OAT retention of ≥12 weeks, and ≥8 weeks for sensitivity analysis. We fit a generalized linear mixed model to the overall study population, and on stratified samples of those continuously engaged on combination antiretroviral therapy (≥95% ART adherence). A set of monthly indicator variables (months 1, …, 7, >7) were included to fulfil the study objective.
Results: Our study included 1427 HCV/HIV co-infected PWID (39.0% female, 68.8% OAT-naïve). The odds of subsequent twelve-week retention in OAT were statistically significantly greater in month 3 versus month 1 (adjusted odds ratio: 1.18; 95% confidence interval: 1.02, 1.37); and the odds of subsequent 8-week retention in OAT were statistically significantly greater in month 2 versus month 1 (1.15, 95% CI: 1.02, 1.31). Among continuously ART-adherent individuals, the odds of subsequent twelve-week retention were not statistically significantly greater than in month 1 (month 2: 1.12 (0.82, 1.51); month 3: 1.08 (0.79, 1.47); month 4: 1.24 (0.91, 1.71)).
Conclusion: We provide evidence that among HCV/HIV co-infected PWID, those retained in OAT for three or more months had higher odds of completing an additional twelve weeks of OAT, compared to no difference in those already receiving ART. These data may have implications for adherence to DAA therapy and further studies are needed to understand the optimal timing of DAA therapy in PWID receiving and not receiving OAT.
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