Hepatitis B two-pair half includes five items: hepatitis B surface antigen (HBsAg) and hepatitis B surface antibody (anti-HBs), hepatitis B e antigen (HBeAg) and hepatitis B e antibody (anti-HBe), and hepatitis B core antibody (anti-HBC). HBsAg and anti-HBs: HBsAg can be positive after 2 weeks of hepatitis B virus (HBV) infection, reflecting presenting hepatitis B virus infection, but a negative test cannot exclude HBV infection. HBsAg itself is only antigenic and not infectious. Anti-HBs starts to appear in the late stage of acute infection, some time after HBsAg turns negative, and gradually rises to a peak within 6-12 months, which can last for many years, but the titer will gradually decrease; anti-HBs can be detected in about half of the cases several months after HBsAg turns negative; a few cases never produce anti-HBs after HBsAg turns negative. anti-HBs positivity indicates immunity to hepatitis B virus Anti-HBs positivity indicates immunity to hepatitis B virus and is seen in recovery from hepatitis B, previous infection and after hepatitis B vaccination. HBeAg and anti-HBe: HBeAg is generally only found in HBsAg positive sera and its presence indicates that the patient is in a high infection low response period. the disappearance of HBeAg and the production of anti-HBe is called e antigen seroconversion. after anti-HBe positive conversion, viral replication is mostly in a quiescent state and infectiousness is reduced. Anti-HBC: Anti-HBC can be detected in almost all HBV-infected patients. Anti-HBCIgM is an antibody that appears earlier after HBV infection, and positivity indicates acute phase or acute attack of chronic hepatitis. Therefore: Hepatitis B two-to-one is a preliminary test used to determine whether or not one is infected with hepatitis B or to roughly estimate the level of viral replication, and different combinations of hepatitis B two-to-one are commonly used clinically to determine the current status and regression of infection.