The hepatitis B virus antigen (HBe antibody/HBe Ab) test is a serological immunoassay that measures the presence of antibodies (usually IgG) directed against the hepatitis B virus antigen (HBeAg). This antibody typically appears after HBeAg has disappeared from the blood. A conversion of HBeAg to HBeAb (called serological conversion) is an important marker of reduced viral replication and improved disease in patients with chronic hepatitis B, whether spontaneous or due to treatment.