Hepatitis B 245 positive refers to items 2, 4 and 5 of the hepatitis B two-to-one test, that is, the three antibodies of hepatitis B surface antibody, e antibody and core antibody are positive, indicating that the hepatitis B virus has been infected in the past, but has now cured itself and has developed immunity to hepatitis B. The hepatitis B two-to-one test is the most commonly used serum marker for detecting hepatitis B virus infection in domestic hospitals, and the items include surface antigen (HBsAg) and surface antibody (anti-HBs or HBsAb), e antigen (HBeAg) and e antibody (anti-HBe or HBeAb), and core antibody (anti-HBc or HBcAb). Because hepatitis B core antigen mostly exists in liver cells and is not easily detected in serum, it is usually not done clinically. Therefore, in the five tests for hepatitis B, the first four items are two pairs and the core antibody is half a pair, so it is called hepatitis B two-and-a-half, and the purpose of the test is to screen for hepatitis B infection and the specific circumstances of the infection. We often use the results of the five tests to distinguish between major and minor hepatitis B, and to initially determine how infectious hepatitis B is. When the hepatitis B virus invades the body, the body produces protein substances to resist it, which we call antibodies. The different component antigens of the virus stimulate the body to produce specific corresponding antibodies, namely hepatitis B surface antibody, e antibody and core antibody, which are antibodies produced by the body against the surface antigen, e antigen and core antigen of the hepatitis B virus respectively. Of these three types of antibodies, only surface antibodies have a protective effect on the body. Surface antibodies generally appear after the surface antigen has disappeared, meaning that the body has cleared the virus and developed resistance to it. In addition, surface antibodies are also produced in the body after hepatitis B vaccination, which means that the vaccination is successful and the body will not be infected with hepatitis B again. Hepatitis B e antibodies generally appear after the e antigen has disappeared, signifying that the replication of the hepatitis B virus has changed from active to relatively quiescent (except when the virus mutates). People who have been infected or are infected will have a positive hepatitis B core antibody. Therefore, only hepatitis B 245 positive, i.e. hepatitis B surface antibody, hepatitis B e antibody, hepatitis B core antibody positive, surface antigen negative, indicates that the person has been infected with hepatitis B in the past, but the body has cleared the virus and will not be infected with hepatitis B again.