Diagnosis of acute or recent hepatitis A virus (HAV) infection. The assay is chemiluminescent microparticle immunoassay (CMIA) for the qualitative detection of IgM antibody to hepatitis A virus (IgM anti-HAV) in human serum and plasma. Serological diagnosis of acute viral hepatitis A depends on the detection of specific anti-HAV IgM. Its presence in the patients serum indicates a recent exposure to HAV. Anti-HAV IgM becomes detectable in the blood within 2 weeks after infection, persisting at elevated levels for about 2 months before declining to undetectable levels by 6 months. However, sensitive immunoassays may occasionally detect anti-HAV IgM for up to 1 year after acute hepatitis A.