Hepatitis A Antibody, IgM

Hepatitis A Antibody, IgM (anti-HAV IgM; HAVAb, IgM) is used to aid in diagnosing acute or recent hepatitis A virus infection by qualitatively detecting HAV-specific IgM. It is appropriate for patients with clinical signs or laboratory findings suggestive of acute hepatitis or following suspected exposure, and it is not intended for routine population screening. Restricting testing to patients with compatible symptoms or exposure history helps minimize false-positive results. IgM anti-HAV typically becomes detectable 2–3 weeks after infection and persists for several months (2–6 months). In contrast, IgG anti-HAV develops later and indicates past infection or immunity.

Hepatitis A is acquired primarily through the fecal–oral route via contaminated food or water or through close contact with an infected person. The resulting hepatic inflammation disrupts bilirubin and nitrogenous waste handling, commonly producing increased serum bilirubin and elevated liver enzyme activities. IgM antibodies to HAV generally become detectable about 2–3 weeks after infection and remain present for 2–6 months, while IgG anti-HAV appears later and usually persists for life. This assay is not cleared or approved for screening blood or plasma donors. Performance characteristics have not been established for immunocompromised or immunosuppressed patients, cord blood, patients younger than 2 years, or cadaveric specimens.