The HBsAg (Hepatitis B Surface Antigen) test detects the presence of the surface antigen of the Hepatitis B virus (HBV) in the blood. HBsAg is a protein found on the outer surface of the Hepatitis B virus and is the earliest indicator of an active Hepatitis B infection. It appears in the blood within 1 to 10 weeks after exposure to the virus.
This test is the primary screening tool for Hepatitis B infection. A positive result indicates that the person is currently infected with HBV and is capable of transmitting the virus to others. It is used to screen blood donors, pregnant women (to prevent mother-to-child transmission), healthcare workers, and individuals at high risk of HBV exposure. If HBsAg remains positive for more than 6 months, it indicates a chronic Hepatitis B infection.
