What does a positive HBsAg indicate in a patient?

A positive HBsAg result indicates an active hepatitis B infection. This means that the hepatitis B virus is present in the blood, and the immune system has not successfully cleared the virus. The presence of HBsAg signifies that the virus is actively replicating, which can lead to liver inflammation and damage.

This marker is crucial for diagnosing an active infection and understanding the patient's infectious status, guiding appropriate management and treatment options. Monitoring HBsAg levels can also help assess the progression of the infection and the patient's response to treatment over time. In contrast, other markers, such as anti-HBs (antibody to HBsAg), would indicate immunity to the virus, either from vaccination or recovery from a previous infection, rather than indicating an active infection.