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%).(ABSTRACT TRUNCATED AT 250 WORDS)