Hepatitis B Virus Tests
Hepatitis B virus (HBV) tests check for substances in the blood that show whether a hepatitis B infection is active or has occurred in the past. The tests look for different signs of infection (markers):
Antigens are markers made by bacteria or viruses. So the presence of HBV antigens means that the virus is in the body.
Antibodies are proteins produced by the body to fight infection. The presence of HBV antibodies means that you have been exposed to the hepatitis B virus at some time. But you could have been infected long ago and gotten better, or you may have a current infection.
- Genetic material (DNA) of the hepatitis B virus shows that the virus is in the body. The amount of DNA can help determine how severe the infection is and how easily the HBV infection can be spread.
It is important to identify the type of hepatitis virus causing infection to prevent its spread and choose the proper treatment.
Hepatitis B virus (HBV) testing
HBV is transmitted through infected body fluids, including blood, semen, and vaginal fluids (including menstrual blood). It also can be transmitted from a pregnant woman to her child at or near the time of birth.
There are several different HBV tests. These are the HBV tests most commonly done:
Hepatitis B surface antigen (HBsAg) is the earliest sign of an active hepatitis B infection. This antigen may be present before symptoms of an HBV infection are present. If this antigen is present for more than 6 months, then you probably have a chronic (long-term) HBV infection. This means you can spread HBV to others throughout your life.
Hepatitis B surface antibody (HBsAb) usually appears about 4 weeks after HBsAg disappears. The presence of this antibody means that the infection is at the end of its active stage and you cannot pass the virus to others (you are no longer contagious). This antibody also protects you from getting HBV again in the future. The test is done to determine the need for vaccination-the antibody will be present after receiving the HBV vaccine series, showing that you have protection (immunity) from the virus. Occasionally your test may show that you have both the HBsAb antibodies and HBsAg antigen. In this case you are still contagious.
Hepatitis B e-antigen (HBeAg) is an HBV protein that is only present during an active HBV infection. This test determines how contagious you are. Testing for this antigen can also be used to monitor the effectiveness of treatment for HBV.
HBV DNA testing checks for genetic material (DNA) from the hepatitis B virus. The HBV DNA tests measure how much genetic material is present. A high level of HBV DNA means that the virus is multiplying in your body and you are very contagious. If you have a chronic HBV infection, an elevated viral DNA level means you are at an increased risk for liver damage and may want to consider treatment with antiviral medicine. Testing for HBV DNA is also used to check the effectiveness of treatment for long-term (chronic) HBV infection. HBV DNA testing is a more sensitive test than HBeAg (above) for detecting HBV in the blood.