IgM antibody to hepatitis C virus in acute and chronic hepatitis C

To assess possible role of testing for IgM‐specific antibody in the diagnosis and monitoring of patients with hepatitis C, we tested sera from 14 patients with acute and 97 patients with chronic non‐A, non‐B hepatitis for IgG and IgM antibody to hepatitis C virus. IgG antibody to hepatitis C virus was detected in 93% of acute cases and 91% of chronic cases. Of the 101 patients with IgG antibody to hepatitis C virus, 57% had IgM antibody to hepatitis C virus. None of the 20 healthy subjects or 40 patients with acute or chronic hepatitis A or hepatitis B had IgM antibody to hepatitis C virus. At the onset of clinical symptoms in acute hepatitis C, IgG antibody to hepatitis C virus was detected in 8 (57%) and IgM antibody to hepatitis C virus in 9 of 14 patients (64%). Eventually, both IgG and IgM antibody to hepatitis C virus became detectable in 13 of 14 patients with acute hepatitis C. Seven patients with antibody to hepatitis C virus resolved the acute infection within 6 mo and all seven cleared IgM antibody to hepatitis C virus, whereas two cleared IgG antibody to hepatitis C virus. Six patients had a chronic outcome of the acute infection and IgM antibody to hepatitis C virus persisted in detectable amounts for more than 6 mo in all (mean = 15.5 mo). Among 88 patients with chronic non‐A, non‐B hepatitis with IgG antibody to hepatitis C virus, IgM antibody to hepatitis C virus was detected in 45(51%). Twenty‐four chronic cases were followed for at least 1 yr: IgM antibody to hepatitis C virus was detected in 13 (54%) at baseline and 8 of these remained positive for at least 1 yr. Patients who lost IgM antibody to hepatitis C virus did not have remission of disease activity. In summary, IgM antibody to hepatitis C virus persists after acute infection in patients who contract chronic hepatitis C; therefore, testing for this antibody may be useful in early identification of patients for antiviral therapy. (HEPATOLOGY 1991;14:38–43.)