A consecutive group of 169 patients with acute hepatitis found negative for hepatitis B surface antigen (HBsAg) and negative for IgM antibody against hepatitis A (anti-HAV IgM) was studied for presence of IgM antibody against hepatitis B core antigen (anti-HBc IgM) by ELISA. Anti-HBc IgM was found in a total of 34 of 60 patients with detectable total anti-HBc. One hundred and nine patients had no detectable anti-HBc IgM and no total anti-HBc and were thus considered as having acute non-A, non-B hepatitis. Among the 34 patients with anti-HBc IgM in their first serum sample, 23 were anti-HBs negative and all had high and steadily decreasing ratio unit (RU) values for anti-HBc IgM (mean RU value 17.1). Twelve of the 23 patients showed seroconversion to anti-HBs during the follow-up, indicating an actual hepatitis B virus infection. Eleven of the 34 anti-HBc IgM positive patients had anti-HBs in their first serum sample. In this group, the RU values for anti-HBc IgM were high and steadily declining and the initial values were significantly lower (mean RU value 9.9) (p < 0.05) than in the anti-HBs negative group. Evidence is provided that anti-HBc IgM in serum from patients with HBsAg negative hepatitis with or without anti-HBs indicates an actual hepatitis B virus infection.
According to generally accepted criteria, the demonstration of anti-HBc IgM identified 20% of the 169 patients with acute non-A, non-B hepatitis as having an actual hepatitis B infection.
Detection of hepatitis B surface antigen (HBsAg) by sensitive radio or enzyme immunoassays in patients with acute hepatitis is in general accepted as a criterion for hepatitis B virus (HBV)-induced disease. Weeks to months after onset of symptoms, the HBsAg usually disappears from the serum and after a variable period, ranging from a few weeks to years, antibody against HBsAg (anti-HBs) can be detected. During this interval, antibody against hepatitis B core antigen (anti-HBc) may be the only serological indicator of the recent HBV infection (1). However, anti-HBc usually persists for several years after the acute episode and is therefore only of ' Other members of the Copenhagen Hepatitis Acuta Programme