Hepatitis B surface antigen (HBsAg) is a coat protein of hepatitis B virus and is not infectious in itself, but its appearance is often accompanied by the presence of hepatitis B virus, so it is a marker of hepatitis B virus infection. It can be present in the patient's blood, saliva, milk, sweat, tears, nasopharyngeal secretions, semen and vaginal secretions. Two to six months after infection with hepatitis B virus, a positive result can be detected in serum 2 to 8 weeks before the elevation of alanine aminotransferase. Most patients with acute hepatitis B can turn negative in the early stage of the disease, and this indicator can be positive for patients with chronic hepatitis B.
Hepatitis B surface antigen usually appears after 1 to 2 weeks of infection with hepatitis B virus, which means hepatitis B virus infection. Hepatitis B surface antigen positive (+) is a marker of HBV infection. If liver function and other HBV infection indicators are normal and only hepatitis B surface antigen is positive, and no symptoms and signs are found, it may be hepatitis B surface antigen carrier or previous hepatitis B. The liver function has returned to normal, but hepatitis B surface antigen Not yet turned negative.