Hepatitis B Core Antibody, IgM

The Hepatitis B Core Antibody, IgM test (anti-HBc IgM; HBV core antibody, IgM) is used with other hepatitis B virus serologic markers to characterize the clinical stage of infection. It assists in evaluating patients with suspected acute viral hepatitis, helps distinguish convalescence from evolution toward chronic infection, and, when considered alongside other HBV markers, contributes to monitoring of chronic hepatitis B for flares.

Hepatitis B virus (HBV) is a DNA virus transmitted through blood and body fluids and remains a global cause of both acute and chronic hepatitis. The core antigen (HBcAg) is strongly immunogenic; anti-HBc IgM appears early, approximately 3–5 weeks after infection. During the late prodromal phase it may be the only specific marker, then typically declines during convalescence, whereas anti-HBc IgG can persist for years. In approximately 9% of acute HBV cases, anti-HBc IgM may be negative in the first two weeks of illness, so repeat testing is warranted in equivocal situations. Detection of HBsAg without anti-HBc IgM supports chronic infection, while emergence of anti-HBc IgM in chronic HBV indicates a flare. A reactive anti-HBc IgM result does not exclude co-infection with other hepatitis viruses, and in patients who are HBsAg positive with hepatitis symptoms but lack anti-HBc IgM, alternative etiologies (e.g., non-A, non-B hepatitis) or hepatitis D virus superinfection should be considered.