The Hepatitis B Surface Antibody Total (Anti-HBs) test is a blood test that detects the presence of antibodies against the Hepatitis B virus surface antigen. The test is used to determine whether a person has been vaccinated against Hepatitis B or has developed immunity to the virus as a result of a previous infection. The surface antigen is a protein that is present on the surface of the Hepatitis B virus and is a target for the body’s immune system to produce antibodies against. The presence of Anti-HBs antibodies indicates that the person has developed immunity to the virus and is protected against future infection. The test is usually ordered for individuals who have received the Hepatitis B vaccine or have a history of Hepatitis B infection to monitor their immunity status. A positive Anti-HBs test result indicates that the person has developed immunity to the virus and is protected against future infection. A negative result suggests that the person is not immune to the virus and may be at risk of infection. The Anti-HBs test is an important tool in the prevention and management of Hepatitis B, and it is often performed alongside other liver function tests and Hepatitis B core antibody tests.