What is the first serological marker that indicates hepatitis B infection?

The first serological marker that indicates hepatitis B infection is HBsAg, or Hepatitis B surface antigen. This antigen is a protein located on the surface of the hepatitis B virus. The presence of HBsAg in the blood signifies an active hepatitis B infection, as it appears early in the course of the disease, often within the first few weeks after exposure to the virus.

Measuring HBsAg levels helps clinicians determine whether a patient is currently infected with hepatitis B, which is crucial for diagnosing and managing the condition. It is the initial marker detected when a person becomes infected, and its presence correlates with viral replication and infectiousness.

Other markers like Anti-HBc IgM appear later in the infection process and are indicative of acute infection, whereas Anti-HBc IgG indicates past infection or chronic hepatitis B. Anti-HBs reflects immunity and recovery from infection but develops after HBsAg has cleared from the blood. This timeline emphasizes the significance of HBsAg as the primary marker for early hepatitis B infection.