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General
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- Pregnant women should be tested for the hepatitis B virus (HBV) early in pregnancy. Individuals who are knowingly exposed to the virus should also be tested.
- Individuals who adopt children from regions of the world where hepatitis B is prevalent are advised to have their children tested when they arrive in the United States. Tests performed in other countries may not always be reliable.
- Tests are performed in a physician's office, a hospital or public health clinic. Many public health clinics offer free testing for HBV and other sexually transmitted diseases (STDs).
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Blood tests
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- Hepatitis B surface antigen (HBsAg): The outer surface of the virus has Hepatitis B surface antigens (HbsAg). Patients who test positive for this antigen can easily pass the virus to others. A negative test means the individual is probably not infected. However, a false–negative result may occur if the test was performed soon after the patient was initially exposed to the virus.
- Antibody to hepatitis B surface antigens (anti–HBs): If individuals have antibodies to HBV, they will test positive for hepatitis B surface antigens. A positive result may indicate that the individual has previously been infected with HBV or the individual has been vaccinated. Patients who test positive cannot become infected.
- Antibody to hepatitis B core antigen (anti–HBc): The blood test for antibodies to the hepatitis B core antigen identifies individuals who have a chronic infection. However, the results can sometimes be ambiguous. Individuals who test positive may have a chronic and contagious infection, or they may be may be recovering from an acute infection or have a slight immunity to HBV that cannot otherwise be detected. The interpretation of this test depends on the results of the other two blood tests.
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Additional tests
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- Once a patient is diagnosed with hepatitis B, a qualified healthcare provider may perform additional tests to determine the severity of the infection and condition of the liver.
- E–antigen test: An E–antigen blood test is used to determine whether a protein that is secreted by HBV–infected cells is present. A positive result means that the patient has high levels of the virus in the blood, and it is very contagious. If the test is negative, the patient has lower levels of HBV in the blood and the virus is less contagious.
- Liver enzymes: Another blood test may be performed to check for elevated levels of liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes leak into the bloodstream when liver cells are injured.
- Alpha–fetoprotein (AFP) test: If the patient has high levels of the alpha–fetoprotein in the blood, it may be a sign of liver cancer. Healthy adult males and non–pregnant females typically have less than 40 micrograms of alpha–fetoprotein per liter of blood.
- Liver ultrasound or computerized tomography (CT) scan: A liver ultrasound or computerized tomography (CT) scan may be performed to detect liver problems. The radiologist analyzes the detailed images of the liver for signs of complications like cirrhosis or liver cancer.
- Liver biopsy: A liver biopsy may be performed to determine the extent of liver damage and to determine the best treatment option for the patient. During the procedure, a needle is inserted into the liver and a small tissue sample is removed. The tissue is then analyzed under a microscope in a laboratory.
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