Helicobacter pylori infection: antibodies to Helicobacter pylori in blood

Normally, IgG antibodies to Helicobacter pylori are absent when qualitatively determined in blood serum; when quantitatively studied, the titer of IgG antibodies is less than 8 U/ml, 8-12 U/ml - “border zone”.

Helicobacter pylori is a gram-negative rod, most often S-shaped. Helicobacter pylori is found in an average of 87% of patients with peptic ulcer disease and 75% of patients with acute gastritis. After the bacteria enter the stomach, they adhere to the cells of the gastric epithelium in the area of intercellular spaces. The latter is due to the chemotaxis of bacteria to the sites of the release of urea and hemin, used for the vital activity of bacteria. Urea, broken down by urease of bacteria, turns into ammonia and carbon dioxide, which create a protective layer around the colonies of bacteria, protecting them from the unfavorable pH of gastric juice.

The following diagnostic methods are used to diagnose Helicobacter pylori.

• Bacteriological:
  • detection of bacteria in smears;
  • Isolation of Helicobacter pylori culture (method sensitivity - 33-97%, specificity - 100%).
• Serological: ELISA, immunoblotting.
• Morphological:
  • histological: detection of bacteria in a biopsy using Romanovsky-Giemsa, Gram, etc. staining (method sensitivity - 86-99%, specificity - 86-95%);
  • cytological: examination of smears-prints (1-2 or more) obtained during endoscopy from biopsies of the antral part of the gastric mucosa (sensitivity of the method is 80-90%, specificity is 100%).
• Biochemical:
  • urease test with biopsies (industrial tests: CLO-test, De-Nol test, PyloriTek, CUT-test, Helpil-test, Campy-test, etc.), the sensitivity of the method is 65-95%, specificity - 75-100%;
  • analysis of exhaled air (an aerotest in which the ammonia content is determined in exhaled air or a more complex analysis of the content of ¹³ C and ¹⁴ C in exhaled air is carried out after the patient has taken urea, previously labeled with the indicated isotopes), the sensitivity of the method is up to 99%, the specificity is 98%.
• IFA:
  • detection of Helicobacter pylori in feces;
  • detection of Helicobacter pylori in saliva and gingival transudate (sensitivity - 66%, specificity - 66.7%).
• PCR.

The most widely used serological method for diagnosing Helicobacter pylori- ELISA method. The method is non-invasive and indirect: antibodies to Helicobacter pylori, classified as IgA, IgM and (most often) IgG, are determined in the patient's blood. When using this method, the most valuable titer of antibodies in the general antibody titer is considered to be the determination of the IgG class titer to Helicobacter pylori. The sensitivity of the method ranges from 87% to 98%, and the specificity is 75-100%. Simple qualitative determination of antibodies to Helicobacter pylori by ELISA is used mainly to diagnose the infection.

In recent years, diagnostic test systems based on ELISA have been developed that have high sensitivity and allow quantitative determination of antibodies to Helicobacter pyloridifferent classes. Such test systems can be used to assess eradication. It has been shown in comparison with invasive methods (histological, urease), that if 30-40 days after treatment the IgG antibody titer values have decreased by 20% or more, it can be considered that Helicobacter pylori has been eradicated as a result of treatment, if the titer value increases, does not change, or its decrease is less than 20%, this should be regarded as the absence of eradication.

Determination of the titer of antibodies to Helicobacter pylori is necessary for the diagnosis of diseases caused by Helicobacter pylori, including gastric ulcer and duodenal ulcer, stomach cancer, and esophageal ulcer.

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