Hepatitis B test: HBSAg in blood

HB _s Ag is normally absent in blood serum.

Detection of hepatitis B surface antigen (HBsAg) in serum confirms acute or chronic HBV infection.

In acute disease, HB _s Ag is detected in the blood serum in the last 1-2 weeks of the incubation period and in the first 2-3 weeks of the period of clinical manifestations. The circulation of HB _s Ag in the blood may be limited to several days, so early primary examination of patients should be sought. The frequency of detection of HB _s Ag depends on the sensitivity of the used research method. The ELISA method allows to detect HB _s Ag in more than 90% of patients. In almost 5% of patients, the most sensitive research methods do not detect HB _s Ag, in such cases the etiology of viral hepatitis B is confirmed by the presence of anti-HB _c IgM. The concentration of HB _s Ag in the blood serum in all forms of severity of viral hepatitis B at the height of the disease has a significant range of fluctuations, at the same time there is a certain pattern: in the acute period there is an inverse relationship between the concentration of HB _s Ag in the serum and the severity of the disease. High concentration of HB _s Ag is more often observed in mild and moderate forms of the disease. In severe and malignant forms, the concentration of HB _{s Ag in the blood is often low, and in 20% of patients with a severe form and in 30% with a malignant form, antigens in the blood may not be detected at all. The appearance of AT to HBs} Ag in patients against this background is considered an unfavorable prognostic sign, it is determined in malignant forms (fulminant) of viral hepatitis B.

In the acute course of viral hepatitis B, the concentration of HB _s Ag in the blood gradually decreases until this antigen disappears completely. HB _s Ag disappears in most patients within 3 months from the onset of acute infection. A decrease in the concentration of HB _s Ag by more than 50% by the end of the 3rd week of the acute period, as a rule, indicates the imminent completion of the infectious process. Usually, in patients with a high concentration of HB _s Ag at the height of the disease, it is detected in the blood for several months. In patients with a low concentration of HB _s Ag, it disappears much earlier (sometimes several days after the onset of the disease). In general, the period of detection of HB _s Ag varies from several days to 4-5 months. The maximum period of detection of HB _s Ag in the smooth course of acute viral hepatitis B does not exceed 6 months from the onset of the disease.

HB _s Ag can be detected in apparently healthy people, usually during preventive or random tests. In such cases, other markers of viral hepatitis B are tested - anti-HB _c IgM, anti-HB _c, anti-HB _e, and the functional state of the liver is studied. If the results are negative, repeated tests for HB _{s Ag are necessary. If HBs} Ag is detected during repeated blood tests for 3 months or more, such a person is classified as a chronic carrier of the surface antigen. Carriage of HB _s Ag is a fairly common phenomenon. There are more than 300 million carriers worldwide, and about 10 million in our country. The cessation of HB _s Ag circulation with subsequent seroconversion always indicates the recovery of the body.

Blood testing for the presence of HB _s Ag is performed for the following purposes:

• Diagnosis of acute viral hepatitis B:
  • incubation period;
  • acute period of the disease;
  • early stage of convalescence.
• diagnosis of chronic carriage of the hepatitis B virus;
• for the following diseases:
  • persistent chronic hepatitis;
  • cirrhosis;
• screening, identification of patients in risk groups:
  • patients with frequent blood transfusions;
  • patients with chronic renal failure;
  • patients with multiple hemodialysis;
  • patients with immunodeficiency states, including HIV infection.

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