During the window period of hepatitis B infection, which serological marker is present?

In the window period of hepatitis B infection, the correct serological marker that is present is the IgM form of the antibody to the hepatitis B core antigen, known as Anti-HBc IgM. The window period refers to the time after HBsAg (hepatitis B surface antigen) has decreased and before anti-HBs (antibodies against HBsAg) has appeared. During this unique phase of infection, the body is mounting an immune response, and IgM antibodies develop as part of that response to the virus.

Presence of Anti-HBc IgM indicates recent infection and is significant for diagnosing acute hepatitis B, especially when the HBsAg is no longer detectable. This timing is crucial for understanding the progression of the infection and for the clinical management of the patient.

While HBsAg is typically present during active infection, its levels can fall during the window period, which is why it is not detected. Anti-HBs only appears after recovery and clearance of the virus, so it would not be present during the window period. HBeAg is also not consistently present during this phase, as its presence usually indicates active viral replication, which may not occur concurrently with the window period findings. Thus, in this specific context of the hepatitis