What Is Hepatitis B Surface Antigen? (HbsAg)
HbsAg is the surface antigen of Hepatitis B virus. If it is present in the blood then it indicates current hepatitis B infection.
The HbsAg test is used to find out whether you have a recent or long-standing infection from the hepatitis B virus (HBV). HBV has proteins called antigens on its surface that cause your immune system to make antibodies. Hepatitis B surface antigens can be found in your blood within several weeks after the infection starts. The HBsAg blood test is used to detect hepatitis B surface antigen (HBsAg).
If you are HBsAg positive, it means you are infectious for the virus and can pass it to other people through your blood or body fluids.
The HBsAg test is used along with other tests to confirm a hepatitis B infection and whether or not the infection is in a contagious state.
What Does Being HbsAg Positive Mean?
HBV is not usually directly cytopathic which means relating to degeneration or disease of cells (although high replication levels in immunosuppressed individuals can lead to direct toxicity) and liver damage is produced by the host’s immune response.
Hepatitis B is an inflammation of the liver caused by a virus. Globally, there are over 400 million chronic carriers of hepatitis B.
Of the 200,000 people who contract hepatitis B , 10 to 15,000 go on to develop a chronic form of the disease. Men are six times more likely than women to become chronic carriers of the hepatitis B virus (HBV), but the reasons for this are unclear.
There are three types of hepatitis B infections:
1. Healthy chronic carriers of hepatitis B are not infectious to others and, although they may have a slightly higher risk of cirrhosis and liver cancer than the general population, they mostly live normal lives. The virus can become reactivated if their immune systems are suppressed,
such as during a severe illness, treatment with immunosuppressant drugs for diseases like cancer or AIDS, or with drugs such as steroids.
2. Chronic infectious hepatitis B is highly infectious. The person with it may have a very inflamed and damaged liver even with few or no symptoms. People with this type of hepatitis B are more likely to have a progressive disease leading to cirrhosis. Only 5% to 10% have spontaneous remission, become non-infectious to others, and sustain no further or minimal liver damage, although sometimes reactivation of the virus occurs.
3. Chronic mutant hepatitis B is a mutated strain of the virus with a permanent alteration of the hepatitis B virus’s genetic makeup.
Those with it have the potential to be infectious to others and it is thought to be more resistant to treatment than other forms of the disease.
What are the Hepatitis B antigens and antibodies?
Hepatitis B virus (HBV) antigens are proteins that appear in different areas of the virus. HBV has three antigens (surface, core, and envelope),
some of which can be detected in the blood. The body’s immune response produces antibodies tailored to each type of antigen (surface antibody, core antibody, and envelope antibody), which can also be detected from a blood test.
- The basic blood test for hepatitis B consists of three screening tests: a hepatitis B surface antigen(HbsAg test), which determines whether a person currently has the infection;
- Hepatitis B core antibody test, which determines whether a person has ever been infected;
- Hepatitis B surface antibody test, which determines whether a person has cleared the virus after infection, or has been vaccinated and is now immune to future infections. These are described below.
What is the Hepatitis B infective status of the HbsAg positive patient?
The HbsAg testscreening test for hepatitis B surface antigens detects the presence of HBV in the blood. The antigens are detectable 4–10 weeks after exposure to HBV. A positive HbsAg test result means the person is currently infected and can pass the infection to others.
Most adults who acquire HBV clear the virus within a few months, and their hepatitis B surface antigen test result will be negative after that time. Some people remain infected and continue to test positive for hepatitis B surface antigen. If, after 6 months, the person still tests positive, his or her HBV infection is considered chronic. People diagnosed with chronic hepatitis B should have a detailed evaluation.
Has the person ever been infected with HBV? The hepatitis B core antibody screening test detects the presence of antibodies to the HBV core antigen.
The antibody appears in the blood within a few weeks of HBV infection. A positive result means the person has been infected with HBV, but it does not specify whether the person has cleared the virus, still has the infection, or is immune to reinfection. Is the person immune to HBV? The hepatitis B surface antibody screening test detects the presence of antibodies the immune system produces to attack the virus. These antibodies appear in people who have been vaccinated against HBV, or who had been infected and cleared the virus from their bodies. A positive hepatitis B surface antibody screening test means the person has lifetime immunity from hepatitis B (the Centers for Disease Control and Prevention [CDC], 2009). In some situations, hepatitis B screening may be unavailable, but the hepatitis B vaccine is available. People can be safely vaccinated against hepatitis B if they have been previously infected or vaccinated.
Hepatitis B Symptoms:
If you have a liver infection caused by HBV. You may need this test if you have symptoms of hepatitis B. Symptoms often start slowly. Many people have no symptoms or only feel like they have a mild case of the flu. You may not have symptoms until the infection becomes severe or chronic.
The most common symptom is extreme tiredness. Other symptoms may include:
- Nausea
- Loss of appetite
- Muscle aches
- Fever
- Yellowed skin and eyes (jaundice)
- Dark-colored urine
- Belly (abdominal) pain
- Swelling and confusion. This is in extreme cases.
Talk to your healthcare provider about being tested for hepatitis B if you feel these symptoms.