The two-and-a-half pair characterization is actually a check for major and minor triplets, i.e., a check for antigens and antibodies expressed in hepatitis B. The two and a half pairs are the two pairs of surface antigen and surface antibody, and E antigen and E antibody. Core antibodies are commonly referred to as two and a half pairs because the antigens cannot be detected and only the antibodies can be detected, which is only half. The hepatitis B triple quantification or hepatitis B triple test is called the hepatitis B two-and-a-half test. The two-and-a-half test is a preliminary determination of the degree of hepatitis B infection or the body’s immune response to hepatitis B infection. At present, the hepatitis B triple test is mainly quantitative, and the two-and-a-half test is mainly qualitative to identify whether the patient is infected with hepatitis B or not. If a patient is determined to have hepatitis B infection after two pairs of semi-qualitative, in addition to judging his immune status, the amount of hepatitis B virus present in the patient’s liver is determined by the surface antigen titer, so as to make a preliminary judgment on the nature and extent of the patient’s hepatitis B infection.