Determination of immunoglobulin M antibodies against hepatitis B core antigen and hepatitis A virus by reorienting sucrose gradient high-speed centrifugation for diagnosis of acute viral-hepatitis.

Immunoglobulin M (IgM) antibodies against hepatitis B core antigen (anti-HBc) and hepatitis A virus (anti-HAV) were determined in 41 cases of acute viral hepatitis. In sera positive for anti-HBc or anti-HAV, IgM was separated from IgG by reorienting sucrose gradient high-speed centrifugation, and the IgG- and IgM-containing serum fractions were tested for the presence of specific antibody by radioimmunoassay. At the onset of illness, 4 of the 41 cases were classified as hepatitis A, 31 were hepatitis B, and 6 were non-A, non-B hepatitis, based on the results of these tests and of assays for hepatitis B surface antigen and antibody and hepatitis B e antigen and antibody. Fourteen of these 41 patients (34%) required IgM anti-HBc or IgM anti-HAV testing or both for appropriate classification. IgM anti-HBc persisted for at least 7 weeks after onset but no longer than 17 weeks in all patients tested with transient hepatitis B surface antigen-positive acute hepatitis. IgM anti-HAV persisted up to but not longer than 62 days in the patients with hepatitis A. Therefore, IgM anti-HBc and IgM anti-HAV determinants are valuable tools for the differential diagnosis of acute A, B, and non-A, non-B hepatitis.