What does having a HepB surface antigen (HBsAg) indicate in a patient?

Having a Hepatitis B surface antigen (HBsAg) indicates that the patient has an active Hepatitis B infection. HBsAg is a protein on the surface of the Hepatitis B virus, and its presence in the serum suggests that the virus is present and replicating in the body. This marker is used to diagnose acute and chronic Hepatitis B infections.

If a patient tests positive for HBsAg, it means they are infected with the virus, and depending on other serologic markers, further evaluations can be made to determine if it is an acute or chronic infection. In cases of acute infection, HBsAg typically appears within a few weeks after exposure and can persist for several months. A patient with chronic viral hepatitis would also remain positive for HBsAg for six months or longer.

In contrast, other options relate to different states of infection or immunization. Immunization against Hepatitis B would result in the absence of HBsAg due to the presence of antibodies (anti-HBs), signifying that the body has developed immunity. Recovery from an acute infection would also show negative HBsAg alongside the presence of antibodies. In chronic viral hepatitis, while HBsAg may be present, this is a specific and direct determination of