If a patient has positive HBsAg and positive IgM anti-HBc, what does this signify?

The presence of positive HBsAg (Hepatitis B Surface Antigen) and positive IgM anti-HBc (Immunoglobulin M antibodies to Hepatitis B core antigen) indicates that the patient is experiencing an acute hepatitis B infection.

HBsAg is the first serological marker to appear in the serum after infection and indicates that the virus is actively replicating. The positive IgM anti-HBc is a marker that specifically indicates recent infection with the virus, typically within the last six months. This combination of serological markers is characteristic of an acute infection, as IgM anti-HBc is not present in chronic infections.

In contrast, chronic hepatitis B infection would typically present with positive HBsAg and the presence of IgG anti-HBc, not IgM. Resolved hepatitis B infection is associated with the presence of anti-HBs and negation of both HBsAg and IgM anti-HBc. Similarly, hepatitis B vaccination would result in the presence of anti-HBs without HBsAg or anti-HBc. Therefore, the combination of markers in this scenario is definitive for an acute hepatitis B infection.