Low prevalence of hepatitis C virus infection in patients with auto-immune hepatitis type 1

Hepatitis C virus (HCV) antibodies were measured in 28 patients with auto-immune hepatitis type 1 using six different assay kits, three for C100–3 antibody and three for second generation HCV antibody, and two confirmatory tests to determine the prevalence of HCV infection in auto-immune hepatitis. These patients were confirmed to have human leucocyte antigen DR 4 or 2 which is susceptible to auto-immune hepatitis in Japanese. Of the 28 patients, four (14.3%) were positive for HCV antibody in all assays and reacted positively in at least one of the two confirmatory tests, indicating a true positive finding. Eight were positive for HCV antibody only by the Ortho ELISA kit and were negative in both confirmatory tests. The cut-off level for these results was low and became negative soon after the patients received corticosteroid treatment. Thus, these eight patients are presumed to be false-positive reactors. Hepatitis C virus RNA was detected in the serum of two of the four patients with HCV antibody and in none of 24 patients without HCV antibody. No significant difference was observed between the patients with and without HCV antibody in terms of clinical background, liver function tests and auto-antibodies. Our results showed that the prevalence of a past or present HCV infection in patients with auto-immune hepatitis in Japan is low; thus, auto-immune hepatitis is thought to be distinct from hepatitis type C. However, it is also suggested that HCV infection can potentially trigger auto-immune hepatitis.