Helicobacter pylori, IgG antibodies

Why this test?

To diagnose diseases caused by H. pylori and control their treatment:

• Antral and fundal gastritis;
• Duodenal or stomach ulcers.

In what cases is it prescribed?

When examining a patient with first-onset signs of dyspepsia (primary H. pylori infection), especially if endoscopy is not planned.

When examining a patient with a history of dyspepsia, if H. pylori therapy was not prescribed (or if antibiotics active against H. pylori were not used for another reason).

At the initial diagnosis of helicobacteriosis and 6 months after the end of the course of its therapy.

Test information

When examining a patient who first developed signs of H. pylori infection, the development of a local and systemic immune response is accompanied. A transient increase in the titer of class M immunoglobulins (IgM) is followed by a long and significant increase in IgG and IgA antibodies in the blood serum. Determination of the concentration of immunoglobulins (serological examination) is used in the diagnosis of helicobacteriosis. IgG is detected in 95-100% of cases of H. pylori infection, IgA - in 68-80%, and IgM - only in 15-20%. Therefore, to confirm H. pylori infection, the concentration of IgG in blood serum is determined. This analysis has a number of advantages over other laboratory methods of bacterial detection.

Determination of IgG in the blood does not require endoscopic examination, therefore it is a safer method of diagnosis. Since the sensitivity of the test is comparable to that of most invasive tests (rapid urease test, histological examination), it is particularly useful when endoscopy is not planned. However, it should be noted that the test does not directly detect the microorganism and depends on the characteristics of the patient's immune response. So, for example, the immune response of the elderly is characterized by a reduced production of specific antibodies (any, including to H. pylori), which must be taken into account if a negative test result is obtained with clinical signs of dyspepsia. In addition, the immune response is suppressed when taking some cytostatic drugs.

IgG analysis can be used with maximum success for the diagnosis of primary H. pylori infection (for example, when examining a young patient with the first signs of dyspepsia). In this situation, a high titer of IgG suggests an active infection. Also, a positive test result in a patient (with or without signs of dyspepsia in the anamnesis) who did not receive therapy will indicate helicobacteriosis.

The interpretation of a positive result of the analysis in the event that therapy was carried out (or if antibiotics with activity against H. pylori were used for other purposes) has some peculiarities. The level of IgG remains high for a long time after the complete death of the microorganism (about half of patients cured of H. pylori will have high titers of IgG for another 1-1.5 years). As a result, a positive result of the analysis in a patient who took antibiotics does not allow to differentiate between an active infection and an infection in the anamnesis and requires additional laboratory tests.

For the same reason, the IgG test is not the main test for diagnosing the effectiveness of therapy. However, it can be used for this purpose if the titer of antibodies at the time of onset of the disease is compared with the titer after the end of treatment. It is believed that a decrease in the concentration of IgG by 20-25% within 6 months indirectly indicates the death of the microorganism. At the same time, if this concentration does not decrease, this does not mean that the therapy is ineffective. The absence of IgG antibodies during repeated analysis indicates the success of the treatment and getting rid of the microorganism.

The amount of IgG to H. pylori is also one of the components by which the condition of the gastric mucosa is judged (this is the so-called serological biopsy).