Understanding the Hepatitis B e-Antigen or HBeAg

What Its Presence Indicates

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HBeAg stands for hepatitis B e-antigen. This antigen is a protein from the hepatitis B virus that circulates in infected blood when the virus is actively replicating. The presence of HBeAg suggests that the person is infectious and is able to spread the virus to other people.

What HBeAg Test Results Mean

A positive test for the hepatitis B e-antigen means that there is an active infection with the hepatitis B virus and the virus is actively multiplying. Anyone who is in contact with your blood without protection may be at risk of contracting hepatitis B from you.

HBeAg Testing During Pregnancy

Pregnant women are screened for a different antigen, the hepatitis B surface antigen (HBsAg) that also show an active infection with hepatitis B. If that test is positive, the HBeAg test may be done, along with tests such as the HBV DNA concentration and alanine aminotransferase (ALT) test for liver health. If the HBeAg test is positive, the Centers for Disease Control and Prevention (CDC) recommends that the woman is referred to a specialist immediately for care until delivery. Whether or not the HBeAg is positive, the newborn will need to be treated with both passive and active immunization (both HBIG and Hepatitis B vaccine), to prevent becoming infected. 

HBeAg in Chronic Hepatitis B

People with chronic hepatitis B can show seroconversion—the levels of HBeAg dropping until they're undetectable while levels of anti-HBe antibodies develop. This is seen as a good sign for prognosis and a sign that your treatment may be working successfully.

Understanding Hepatitis B e-Antigen

An antigen is a protein that stimulates an immune system response, causing your body to produce antibodies to fight invaders. In hepatitis B, it's common to test for the hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg). These antigens are attached to the inside and the outside of the virus.

The hepatitis B e-antigen is different. It's a protein that the virus manufactures and secretes. It isn't circulating while attached to the virus but instead is free in your bloodstream and tissues. It's produced when the virus is actively multiplying, so it's a sign that you have an active infection and people in contact with your blood and body fluids are at risk of catching the infection.

Interestingly, there are strains of hepatitis B virus that don't produce HBeAg. People who acquire the infection in the Middle East and Asia may have one of these strains. In this case, a negative HBeAg test has little meaning. They can have an active Hepatitis B infection without a positive HBeAg test.

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  1. Liaw YF. HBeAg seroconversion as an important endpoint in the treatment of chronic hepatitis B. Hepatol Int. 2009;3(3):425-33. doi:10.1007/s12072-009-9140-3

  2. Centers for Disease Control and Prevention (CDC). Screening and Referral Algorithm for Hepatitis B Virus (HBV) Infection Among Pregnant Women. U.S. Department of Health and Human Services. Published March 2015.

  3. McHugh JA, Cullison S, Apuzzio J, et al. Chronic Hepatitis B Infection: a Workshop Consensus Statement and Algorithm. The Journal of Family Practice. September 2011;60(9):E1-8.

  4. American Association for Clinical Chemistry. Hepatitis B Testing. Lab Tests Online. Updated March 5, 2014.

Additional Reading

  • American Association for Clinical Chemistry. Hepatitis B Testing. Lab Tests Online. Updated March 5, 2014.