Significance of IgM antibody to hepatitis C virus in patients with chronic hepatitis C

We assessed the correlation between the positivity for serum IgM antibody to hepatitis C virus and the activity of liver disease in patients with chronic hepatitis C virus infection. Serum samples were taken from 10 antibody to hepatitis C virus‐positive asymptomatic patients with normal serum ALT levels, from 14 untreated patients with clinically and histologically proven chronic hepatitis C and from 26 patients with clinically and histologically proven chronic hepatitis C assigned to receive recombinant interferon α‐2a (6 million IU three times a week for 6 mo). Each serum specimen was tested for IgM antibody to hepatitis C virus‐associated C 100‐3 antigen by enzyme‐linked immunosorbent assay. Patients were observed for at least 12 mo. All 10 patients with normal ALT values tested negative for IgM antibody to hepatitis C virus. In contrast, 33 of 40 (82%) patients with chronic hepatitis C had IgM antibody to hepatitis C virus, and a positive correlation was seen between the ALT level and the level of IgM antibody to hepatitis C virus (r = 0.803, p < 0.001). During interferon treatment, ALT levels declined into the normal range in 18 of 26 treated patients (69%) and remained normal after stopping treatment in 8 patients (31%). In untreated patients, in treated patients who did not respond to interferon treatment and in responder patients who relapsed, no significant changes in IgM antibody to hepatitis C virus levels were seen during the study period. In contrast, IgM antibody to hepatitis C virus became undetectable by the end of interferon treatment in seven of eight patients with a sustained response. In conclusion, we found a positive correlation between the presence of serum IgM antibody to hepatitis C virus and the activity of the hepatitis C‐induced liver disease. In patients with chronic hepatitis C showing a response to α‐interferon treatment, the disappearance of IgM antibody to hepatitis C virus predicted that the response would be sustained. (H EPATOLOGY 1992;15:998–1001).