The hepatitis B core antigen is an antigen that can be produced by the hepatitis B virus, because it cannot be detected from the blood, so it needs to be detected by other methods, in the clinic is to determine the presence or absence of hepatitis B core antigen by detecting the presence or absence of hepatitis B core antibody. The hepatitis B core antigen and the core antibody are a pair. After the hepatitis B virus invades the body, the immune system will produce core antibodies when it sees the hepatitis B core antigen, so the presence or absence of core antibodies can be used to determine the presence or absence of the core antigen. The core antigen exists only in the hepatitis B virus. If the core antibody test is positive, it means that the body has been infected with the hepatitis B virus, so it can be seen if the person is a hepatitis B patient. But this can only be seen before is not, if hepatitis B is cured, this core antibody will still be positive, so the core antigen of hepatitis B is mainly this meaning.