A transient positive association between direct‐acting antiviral therapy for hepatitis C infection and drug‐related hospitalization among people who inject drugs: Self‐controlled case‐series analysis of national data

Abstract

Background and aimsDirect‐acting antiviral (DAA) treatment has an established positive effect on liver outcomes in people with hepatitis C infection; however, there is insufficient evidence regarding its effects on the ‘extra‐hepatic’ outcomes of drug‐related hospitalization and mortality (DRM) among people who inject drugs (PWID). We investigated associations between these outcomes and DAA treatment by comparing post‐treatment to baseline periods using a within‐subjects design to minimize selection bias concerns with cohort or case–control designs.DesignThis was a self‐controlled case‐series study.SettingScotland, 1 January 2015–30 November 2020.ParticipantsThe study population of non‐cirrhotic, DAA‐treated PWID was identified using a data set linking Scotland's hepatitis C diagnosis, HCV clinical databases, national inpatient/day‐case hospital records and the national deaths register. Three principal outcomes (drug overdose admission, non‐viral injecting related admission and drug‐related mortality) were defined using ICD codes.MeasurementsSelf‐controlled case‐series methodology was used to estimate the relative incidence (RI) of each outcome associated with time on treatment and up to six 90‐day exposure risk periods thereafter.FindingsA total of 6050 PWID were treated with DAAs in the sampling time‐frame. Compared with the baseline period, there was a significantly lowered risk of a drug overdose hospital admission in the second to fifth exposure risk periods only [relative incidence (RI) = 0.86, 95% confidence interval (CI) = 0.80–0.99; 0.89, 95% CI = 0.80–0.99; 0.86, 95% CI = 0.77–0.96; 0.88, 95% CI = 0.78–0.99, respectively]. For non‐viral injecting‐related admission, there was a reduced risk in the first, third and fourth exposure risk periods (RI = 0.76, 95% CI = 0.64–0.90; 0.75, 95% CI = 0.62–0.90; 0.79, 95% CI = 0.66–0.96, respectively). There was no evidence for reduced DRM risk in any period following treatment end.ConclusionsAmong people who inject drugs in Scotland, direct‐acting antiviral treatment appears to be associated with a small, non‐durable reduction in the risk of drug‐related hospital admission, but not drug‐related mortality. Direct‐acting antiviral therapy, despite high effectiveness against liver disease, does not appear to offer a panacea for reducing other drug‐related health harms.