Effect of hepatitis C virus treatment engagement on the skin and soft tissue infections healthcare burden among people who inject drugs in Quebec, Canada: a population-based interrupted time series study

BACKGROUND: Hepatitis C virus (HCV) and skin and soft tissue infections (SSTIs) are common among people who inject drugs (PWID) and represent a considerable burden for individuals and healthcare systems. Engagement in HCV treatment may have positive spillover effects, reducing rates of other health outcomes and healthcare utilization. We aimed to examine such effects among PWID living with HCV. METHODS: We used Quebec's Public Health Mandatory Reportable Infectious Disease database, which links reported HCV cases with laboratory and administrative health data to create a population-based cohort of HCV cases. A validated algorithm identified PWID. Using inverse probability treatment weighting and a balanced interrupted time series with control, we compared SSTI diagnoses, SSTI hospitalizations, and all-cause hospitalizations among PWID who engaged in HCV treatment between 2014 and 2018, inclusive, to those who did not. RESULTS: Among 3786 eligible HCV-RNA positive PWID, 996 (26%) engaged in treatment. Post-treatment engagement, there was an immediate decline in monthly SSTI diagnoses and hospitalizations (-1395 [95% CI: -2466, -325]) and (-336 [95% CI: -657, -15]) per 100,000 individuals, respectively, in the treated compared with counterfactual PWID. Post-treatment engagement reduction in SSTI outcomes was sustained over three years (no trend effects). The effect of treatment engagement on all-cause hospitalizations was uncertain (-895 [95% CI: -1936, 147] per 100,000 individuals). INTERPRETATION: HCV treatment engagement has an immediate and sustained effect on reducing SSTI diagnoses and hospitalizations, suggesting that treatment may provide an opportunity to address other burdensome health issues. Given the low treatment initiation rate observed, scaling up HCV treatment among PWID could have a large impact on reducing the healthcare burden associated with injection drug use.