Presence and meaning of anti-HBc IgM as determined by ELISA in patients with acute type B hepatitis and healthy HBsAg carriers.

To evaluate the clinical implication of IgM antibody against hepatitis B core antigen (anti-HBc IgM), a consecutive series of 87 patients with acute type B hepatitis and 16 healthy carriers of hepatitis B surface antigen (HBsAg) were studied by a newly developed reverse ELISA technique. Anti-HBc IgM was present for at least 2 months in 81 of the 82 patients with HBsAg at the time of admission. Seroconversion from HBsAg to anti-HBs was observed in 38 patients during the time of observation, and in all patients, anti-HBc IgM was present until clearance of HBsAg. Thirty-three of the 38 patients remained anti-HBc IgM positive, at least until the appearance of anti-HBs. Quantitation of anti-HBc IgM by ratio unit (RU) values revealed that 3 of 8 patients with RU values greater than or equal to 5 for more than 6 months subsequently developed chronic liver disease, as compared to 1 of 72 patients with anti-HBc IgM above this level for less than 6 months. Anti-HBc IgM was demonstrated in 3% of 5 patients with total anti-HBc titer above 1:100 despite the presence of anti-HBs. In these patients, anti-HBc IgM steadily decreased after the onset of illness indicating a recent acute hepatitis B infection. Anti-HBc IgM was present in 12 of 16 healthy HBsAg carriers (75%). However, these 12 carriers had RU values between 2.5 to 5.5, compared with RU values above 5 (mean RU value 11.3) at the onset of illness in 80 of 82 HBsAg-positive patients with acute hepatitis. Anti-HBc IgM seems to be a specific serological marker for recent or ongoing hepatitis B infection which may be useful in differentiation between hepatitis B infection with or without HbsAg and acute non-A, non-B hepatitis.