Hepatitis B Virus Tests

HBV Antibody Tests

Test Overview

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 indicator of an active hepatitis B infection. This antigen may be present before symptoms of an HBV infection are present. If this antigen level remains high for more than 6 months, then you will probably become a carrier of HBV, meaning you can transmit it 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 and HBsAg antibodies. 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, 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 monitor the effectiveness of treatment for chronic HBV infection. HBV DNA testing is a more sensitive test than HBeAg (above) for detecting HBV in the blood.

Other HBV tests are not done as often:

• Hepatitis B core antibody (HBcAb) is an antibody to the hepatitis B core antigen that appears about 1 month after an active HBV infection. It can be found in people who had an infection in the past and in those with long-term (chronic) HBV. It usually is present for life. Blood banks test for this antibody when screening donated blood for hepatitis B.
• Hepatitis B core antibody IgM (HBcAbIgM) is another antibody to the hepatitis B core antigen. It indicates an HBV infection that has occurred within the last 6 months.
• Hepatitis B e-antibody (HBeAb) shows that the active stage of an acute HBV infection is almost over, and your risk of being contagious is greatly reduced.

A hepatitis B vaccine is available to prevent an HBV infection.

Hepatitis D virus (HDV) testing

Infection with the hepatitis D virus (HDV), or delta agent, occurs only in people who are already infected with the hepatitis B virus (HBV). Vaccination against hepatitis B will prevent hepatitis D infection. Hepatitis D infection is rare in the United States and Canada, except among people who inject illegal drugs and those who are frequently exposed to blood products. The hepatitis D test detects HDV antibodies. A positive test indicates only that you have been infected with HDV—it cannot distinguish between an acute or chronic infection. Another test, the HDV RNA test, is needed to determine whether you have an active HDV infection. It does not distinguish between an acute or chronic infection. This test currently is not available except in research settings.

Since hepatitis B infections can be spread through sexual contact, practice safe sex until your test results are returned.

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Author:	Maria G. Essig, MS, ELS	Last Updated: October 15, 2007
Medical Review:	Kathleen Romito, MD - Family Medicine W. Thomas London, MD - Hepatology
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