What does a positive HBsAg and negative HBs antibody indicate?

A positive HBsAg (Hepatitis B Surface Antigen) combined with a negative HBs antibody (anti-HBs) indicates the presence of the hepatitis B virus in the bloodstream, which is characteristic of an active infection. This scenario is typically seen in chronic hepatitis B infection, where the virus persists in the body over a prolonged period, often leading to ongoing liver inflammation and potential liver damage.

In cases of chronic infection, the body may not develop sufficient antibodies to the surface antigen, resulting in the HBsAg remaining positive while the antibodies are absent. This situation suggests that the individual has not cleared the virus and may continue to be infectious.

It is important to distinguish this condition from other scenarios, such as acute hepatitis infection, where HBsAg would also be positive but would be expected to have all antibodies produced as the infection resolves. In the case of resolved hepatitis infection, the antibodies would be positive, indicating that the body has successfully cleared the virus. Vaccination against hepatitis B would also show a positive anti-HBs result without the presence of HBsAg, indicating immunity rather than active infection. Thus, the specific combination of positive HBsAg and negative anti-HBs is most consistent with a chronic hepatitis infection.