Radioimmunoassay detection of IgM antibodies to the hepatitis B core antigen in HBsAg liver disease.

A radioimmunoassay is described for detection of IgM antibody to the hepatitis B core antigen. The assay is based on the selective absorption of IgM immunoglobulins from test serum by anti-IgM fixed on a solid phase, followed by incubation with HBcAg and radiolabeled anti-HBc of IgG type. IgM anti-HBc was found in high titers in all the patients with acute hepatitis B; in two of four patients whose acute hepatitis progressed to chronicity, IgM anti- HBc disappeared in 4-6 months despite continuing HB viremia. IgM anti-HBc was also found in low titers in 19% of the patients with chronic HBV infection. No relation was noted between the presence of IgM anti-HBc and clinical or serological categories of chronic carriers of the HBsAg. The antibody was not found in carriers with hepatitis caused by superinfection with the hepatitis A virus or the HBV-associated delta agent. IgM anti-HBc is a marker of a recent HBV infection. Its absence in HBsAg-positive individuals with acute hepatitis should rise suspicion that the patients are carriers of the HBsAg experiencing disease caused by factors other than the HBV.