Pennsylvania Health Department Reports 2 Additional Measles-Related Deaths

Hepatitis B surface antigen, commonly known as HBsAg, is a protein found on the surface of the hepatitis B virus. This antigen appears in the blood during an active hepatitis B infection, whether the infection is acute or chronic. The HBsAg test is one of the most important blood tests used to diagnose hepatitis B virus infection and to screen for the disease in people who may have been exposed to the virus. Healthcare providers order this test when someone shows symptoms of hepatitis, has been exposed to the virus, or as part of routine screening for high-risk individuals.

When HBsAg is detected in the blood, it indicates that the person is currently infected with hepatitis B virus and can potentially transmit the infection to others. If HBsAg remains detectable in the blood for more than six months, the infection is considered chronic. A negative HBsAg result generally means that a person is not currently infected with hepatitis B, though additional tests may be needed to determine if someone has recovered from a past infection or has been successfully vaccinated. The test is particularly important for pregnant women, healthcare workers, people with multiple sexual partners, and individuals who inject drugs, as these groups face higher risks of hepatitis B infection.

The HBsAg test is typically performed using a blood sample drawn from a vein in the arm. The sample is then analyzed in a laboratory using immunoassay techniques that detect the presence of the surface antigen. No special preparation is usually required before the test, and results are typically available within a few days. If the test is positive, doctors will usually order additional tests to determine whether the infection is acute or chronic and to assess liver function. These follow-up tests may include hepatitis B e antigen, hepatitis B core antibody, hepatitis B surface antibody, and liver enzyme tests.

Understanding HBsAg test results is crucial for appropriate medical management. A positive result requires medical follow-up to monitor liver health and determine if antiviral treatment is necessary. People with chronic hepatitis B need regular monitoring to prevent complications such as liver cirrhosis and liver cancer. A negative HBsAg result in someone who has been vaccinated, combined with positive hepatitis B surface antibodies, indicates successful immunization and protection against the virus. Early detection through HBsAg testing allows for timely intervention and helps prevent the spread of hepatitis B to others.