A positive result for HBsAg means what?

A positive result for HBsAg indicates an active hepatitis B virus infection. HBsAg, or hepatitis B surface antigen, is a protein present on the surface of the hepatitis B virus. Its presence in the blood signifies that the virus is actively replicating and the individual is currently infected. This means they can transmit the virus to others and may experience symptoms related to hepatitis B infection, which can vary from mild to severe.

In contrast, the other options describe different states of hepatitis B infection or immunity. Immunity to hepatitis B, often resulting from either past infection or vaccination, would be indicated by the presence of antibodies to HBsAg rather than the antigen itself. Similarly, being recently vaccinated against hepatitis B would not produce a positive HBsAg result, but would instead result in the development of antibodies over time. Lastly, a past infection would typically show the presence of antibodies, rather than the antigen, indicating a resolved infection. Therefore, the correct interpretation of a positive HBsAg result is that the individual is currently infected with hepatitis B.