What does HBsAg detect in a patient's blood?

The detection of HBsAg, or Hepatitis B surface antigen, in a patient's blood indicates the presence of the hepatitis B virus (HBV). It serves as an important marker for active infection. When HBsAg is present, it signifies that the person is currently infected with HBV, which can result in either an acute or chronic infection. This marker is crucial for diagnosing hepatitis B and helps healthcare providers determine the appropriate management and monitoring of the disease.

Understanding the significance of HBsAg is essential for healthcare professionals, as it informs them about the patient's infection status and potential contagiousness. If HBsAg is negative, it usually indicates that the patient does not have an active infection, which can guide further testing for immunity or previous exposure to the virus.