HBsAG stands for hepatitis B surface antigen.

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HBsAG stands for hepatitis B surface antigen. When a healthcare provider orders blood tests to determine if someone is infected with the hepatitis B virus, one thing he is looking for is HBsAG in the blood. If it is found, along with other specific antibodies, it means the person has a hepatitis B infection.

Hepatitis B


Hepatitis B is a serious liver infection caused by the hepatitis B virus (HBV).

For some people, hepatitis B infection becomes chronic, meaning it lasts more than six months. Having chronic hepatitis B increases your risk of developing liver failure, liver cancer or cirrhosis — a condition that causes permanent scarring of the liver.

Most people infected with hepatitis B as adults recover fully, even if their signs and symptoms are severe. Infants and children are more likely to develop a chronic hepatitis B infection. A vaccine can prevent hepatitis B, but there's no cure if you have it. If you're infected, taking certain precautions can help prevent spreading HBV to others.


Signs and symptoms of hepatitis B, ranging from mild to severe, usually appear about one to four months after you've been infected. Signs and symptoms of hepatitis B may include:

  • Abdominal pain
  • Dark urine
  • Fever
  • Joint pain
  • Loss of appetite
  • Nausea and vomiting
  • Weakness and fatigue
  • Yellowing of your skin and the whites of your eyes (jaundice)


    The Hepatitis B virus is passed from person to person through blood, semen or other body fluids.

    Common ways HBV is transmitted include:

    • Sexual contact. You may become infected if you have unprotected sex with an infected partner whose blood, saliva, semen or vaginal secretions enter your body.
    • Sharing of needles. HBV is easily transmitted through needles and syringes contaminated with infected blood. Sharing intravenous (IV) drug paraphernalia puts you at high risk of hepatitis B.
    • Accidental needle sticks. Hepatitis B is a concern for health care workers and anyone else who comes in contact with human blood.
    • Mother to child. Pregnant women infected with HBV can pass the virus to their babies during childbirth. However, the newborn can be vaccinated to avoid getting infected in almost all cases. Talk to your doctor about being tested for hepatitis B if you are pregnant or want to become pregnant.

    More About HBsAG

    HBsAG, which is cleared within 4 to 6 months in self-limited infections (infections that resolve by themselves), can be detected in the blood during both acute infections (infections that come on suddenly) and chronic infections (infections that last for longer than 6 months). In addition to the signs and symptoms that a patient has, additional antibodies can be tested to distinguish between acute and chronic infections.

    At the center of the hepatitis B virus is DNA, which contains the genes the virus uses to replicate itself. Surrounding the DNA is a protein called HBcAG (hepatitis B core antigen), which cannot be detected with blood tests.

    Surrounding this is HBsAG, which is actually part of the protective "envelope." This envelope surrounds the virus and protects it from attack by the body's immune system. However, this system is good at getting through this envelope in order to kill the virus. When it does, remnants of surface antigen protein are left in the blood like debris, which lab tests can detect.


    Mayo Clinic. Hepatitis B. http://www.mayoclinic.org/diseases-conditions/hepatitis-b/basics/definition/con-20022210

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