Learn about the HBsAg Test , its purpose, uses, normal values, test results interpretation, and more for a better understanding of your health. Get complete information on the HBsAg Test : Procedure, uses, results interpretation, and normal range. Understand how this test is used to diagnose. The Hepatitis B Surface Antigen ( HBsAg) test is a crucial diagnostic tool used in the field of clinical laboratory medicine to detect the presence of the Hepatitis B virus (HBV) in an individual’s bloodstream. Hepatitis B is a viral infection that primarily affects the liver, and HBsAg is a key marker of this infection. The Hepatitis B Surface Antigen ( HBsAg) Test is a blood test used to detect the presence of a protein on the surface of the Hepatitis B virus. It's the primary screening test to diagnose Hepatitis B infection and assess whether someone is currently infected with the virus. Hepatitis B Surface Antigen Test Here are the basic details of the Hepatitis B Surface Antigen Test .