Hepatitis B virus, surface antigen (HbsAg), quantitatively
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Why this test?
For screening of infection in the absence of symptoms of the disease.
To find out whether the disease is acute or chronic.
To control chronic hepatitis B.
To test for hepatitis B in risk groups or blood donors.
To detect previous infections (in case of acquiring subsequent immunity).
To find out, developed immunity after vaccination
In what cases is it prescribed?
When the patient has symptoms of acute hepatitis: fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine, pale stool, joint pain, jaundiced skin.
When screening patients from categories of increased risk of hepatitis B infection.
- health care workers who can become infected as a result of accidental cuts, injections, etc.;
- people born in regions where the prevalence of HBsAg reached more than 2% (most Asian and African countries);
- did not get vaccinated against hepatitis in a timely manner;
- those whose parents come from regions where HВsAg prevalence exceeds 8%;
- patients with elevated liver enzyme activity (ALT and AST) for unknown reasons;
- patients with diseases that require suppression of their immune system;
- being in close contact with those infected with HBV;
- AIDS patients;
- every 6-12 months when monitoring the condition of patients suffering from chronic hepatitis B;
- before any blood transfusion.
The HBV virus is a common cause of hepatitis B. It is believed that the true number of infected people exceeds the official statistics, as many of those infected experience only mild symptoms and do not suspect that they are affected by the virus.
In the world, about 350 million people are infected with hepatitis and about 620 thousand die from it every year. The HBV virus spreads through contact with the blood or other physiological fluids of an infected person. It is possible to become infected, for example, through the use of the same needle from a syringe or through unprotected sexual contact.
Traveling to places where hepatitis B is common is also dangerous. A mother can infect her child during or after childbirth. However, the virus is not transmitted through food and water, as well as through everyday contacts: shaking hands, coughing or sneezing.
Tests for bilirubin and liver function detect hepatitis, but do not reveal its cause. It is the analysis of HBsAg in the blood that determines hepatitis B and the HBV virus that causes it. The hepatitis B virus is DNA surrounded by a protein capsule - the capsid, which is responsible for the process of introducing the virus into the cells of the body.
The capsid proteins were named HBsAg (from the English hepatitis B surface antigen), HBcAg (hepatitis B core antigen) and HBeAg (hepatitis B capsule antigen). If they are present in the blood, it can be assumed that a person is infected with the virus, so the analysis for the presence of these antigens is a standard method of diagnosing hepatitis B. HBsAg is the surface antigen of the hepatitis B virus. When the virus enters the cell, it begins to produce new DNA chains, multiply and the HBsAg antigen is released into the blood. In acute hepatitis B, it appears in the blood 3-5 weeks after infection (in the last 1-2 weeks of the incubation period) and usually persists until the end of the first 2-3 weeks of clinical manifestations. In chronic hepatitis B, HBsAg is detected in all phases of the course of the disease.
The detection of HBsAg during a screening examination is an indication for consultation with an infectious disease specialist and further examination for other markers of the hepatitis B virus in order to verify the diagnosis and clarify the stage of the disease.