The three systems of hepatitis B refer to hepatitis B surface antigen and hepatitis B surface antibody, hepatitis B e antigen and hepatitis B e antibody, and hepatitis B core antigen and hepatitis B core antibody, which are common markers of hepatitis B. The hepatitis B core antigen is usually hidden in the liver cells and is not detected in the ordinary blood because of its extremely low level. They are usually tested for hepatitis B surface antigen, hepatitis B surface antibody, hepatitis B e antigen, hepatitis B e antibody, and hepatitis B core antibody. The different positivity of these markers and the different combinations have different clinical significance. These hepatitis B markers can reflect whether the body has been infected with the hepatitis B virus, or what state the infection is in.