Objective To elucidate the association between antiviral therapy and extrahepatic outcomes in individuals infected with HCV.

Methods This nationwide cohort study screened 293 480 Taiwanese residents with HCV infection and excluded those with substantial comorbidity. A total of 12 384 eligible patients who had received pegylated interferon plus ribavirin between 1 October 2003 and 31 December 2010 were enrolled in the treated cohort; they were matched 1 : 2 with 24 768 untreated controls in the propensity score and post-diagnosis treatment-free period. The incidences of end-stage renal disease (ESRD), acute coronary syndrome (ACS), ischaemic stroke and catastrophic autoimmune diseases were calculated after adjustment for competing mortality.

Results The treated and untreated cohorts were followed up for a mean (±SD) duration of 3.3 (±2.5) and 3.2 (±2.4) years, respectively, until 31 December 2011. The calculated 8-year cumulative incidences of ESRD, ACS, ischaemic stroke and autoimmune catastrophes between treated and untreated patients were 0.15% vs 1.32% (p<0.001), 2.21% vs 2.96% (p=0.027), 1.31% vs 1.76% (p=0.001) and 0.57% vs 0.49% (p=0.816), respectively. Multivariate-adjusted Cox regression revealed that antiviral treatment was associated with lower risks of ESRD (HR 0.15; 95% CI 0.07 to 0.31; p<0.001), ACS (HR 0.77; 95% CI 0.62 to 0.97; p=0.026) and ischaemic stroke (HR 0.62; 95% CI 0.46 to 0.83; p=0.001), but unrelated to autoimmune catastrophes. These favourable associations were invalid in incompletely treated patients with duration <16 weeks.

Conclusions Antiviral treatment for HCV is associated with improved renal and circulatory outcomes, but unrelated to catastrophic autoimmune diseases.