▪ Objective: To determine whether laboratory findings showing antibodies to hepatitis C virus (HCV) in patients with autoimmune hepatitis represent false-positive results and to identify possible explanations for true-positive results in these patients.
▪ Design: Cross-sectional.
▪ Setting: University-based hospital.
▪ Patients: Fifty-two patients with non-A, non-B chronic hepatitis as a control group and 26 patients with classic chronic active autoimmune hepatitis.
▪ Measurements: Comparison of the results of five kinds of assays of HCV antibodies and HCV RNA.
▪ Main Results: Of 52 patients with non-A, non-B chronic hepatitis, HCV antibodies (anti-HCV) were detected in 42 patients (81%; 95% Cl, 67% to 90%) by a first-generation enzyme-linked immunosorbent assay (ELISA-I), in 39 patients (75%) by Sp42 ELISA, in 37 patients (71%) by RIA-I, in 49 patients (94%) by ELISA-II, and in 48 patients (92%) by RIBA-II. We found HCV RNA in 47 patients (90%; Cl, 79% to 97%). Of the 26 patients with autoimmune hepatitis, anti-HCV were detected in 23 patients (88%; Cl, 70% to 98%) by ELISA-I, in 12 (46%) by both RIA-I and Sp42 ELISA, in 20 (77%) by ELISA-II, and in 9 (35%) by RIBA-II. However, HCV RNA was found in only five of these patients (19%; Cl, 7% to 39%). None of our patients, including controls, had antibodies to superoxide dismutase. Of the 21 patients who had autoimmune hepatitis that was completely responsive to steroid therapy, 18 had anti-HCV by ELISA-I, but 13 of these patients had negative results by RIBA-II, and only two patients had HCV RNA. Of the five patients who did not respond to steroid treatment, all had anti-HCV by ELISA-I, four had negative results by RIBA-II, and three had HCV RNA.
▪ Conclusions: Testing for HCV antibodies in patients with autoimmune hepatitis frequently elicits positive results when the ELISA-I or ELISA-II tests are used. Most of these appear to represent false-positive results because HCV RNA is usually absent from the serum. Such false positivity may result from previous infection with HCV or from cross-reaction of an epitope of HCV. Other patients with apparent autoimmune hepatitis who fail to respond to corticosteroid therapy may actually have chronic hepatitis C (or other non-A, non-B hepatitis) infection.