The two-and-a-half pair test refers to the hepatitis B two-and-a-half pair test, also known as the hepatitis B five-item test. The specific tests include hepatitis B surface antigen, hepatitis B surface antibody, hepatitis B e antigen, hepatitis B e antibody and hepatitis B core antibody. The hepatitis B two-to-one test is one of the first tests for clinical screening of hepatitis B infection. Through the hepatitis B two-to-one test, it is also possible to clarify whether the body produces protective antibodies and the specific stage of hepatitis B, which provides the basis for clinical treatment. Among them, positive hepatitis B surface antigen, hepatitis B e antigen and hepatitis B core antibody refers to hepatitis B major triple yang; positive hepatitis B surface antigen, hepatitis B e antibody and hepatitis B core antibody refers to hepatitis B minor triple yang. These two may appear more obvious viral replication, with a certain degree of infectiousness, may need timely antiviral treatment. For those who are negative for all five items of hepatitis B, they also need timely vaccination against hepatitis B in order to produce surface antibodies and reduce the risk of infection with the hepatitis B virus.