Hepatitis B e-Antigen or HBeAg Definition

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Doctor with Patient. Adam Berry / Stringer / Getty Images

What is the Hepatitis B e-Antigen HBeAg?

 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 Do 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.

The virus is actively multiplying if this antigen is found in your blood. Anyone who is in contact with your blood without protection may be at risk from contracting it from you.

HBeAg Testing During Pregnancy - When and Why is it Done?

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 ALT test for liver health. If the HBeAg test is positive, the CDC recommends that the woman is referred to a specialist immediately for care until delivery. If it is negative, they recommend referring for postpartum care. The baby can be infected during delivery by contact with the mother's blood or body fluids.

HBeAg in Chronic Hepatitis B

People with chronic hepatitis B can show seroconversion - the levels of HBeAg dropping until it is undetectable while levels of anti-HBe antibodies develop.

This is seen as a good sign for prognosis and a sign that treatment may be working successfully.

What is the 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 is common to test for 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 is a protein that the virus manufactures and secretes. It isn't circulating attached to the virus but instead is free in your bloodstream and tissues. It is produced when the virus is actively multiplying, so it is a sign that you have an active infection. It is taken as a sign that you are infectious 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.


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

Apuzzio J, Block J, Cullison S, et al. "Chronic Hepatitis B in pregnancy: A workshop consensus statement on screening, evaluation, and management, part 2. The Female Patient." 2012; 37(5):30-34.

Hepatitis B Testing, Lab Tests Online, February 24, 2015. American Association for Clinical Chemistry.

Yun-Fan Liaw. "HBeAg seroconversion as an important end point in the treatment of chronic hepatitis B." Hepatol Int. 2009 Sep; 3(3): 425–433.

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