2074. Helicobacter pylori (protein CagA), IgM antibodies

Specific IgM antibodies to CagA appear at the early stages of Helicobacter pylori infection and indicate an acute or recent infection. Their detection is useful for early diagnosis of active disease and for assessing the risk of a complicated clinical course.

Helicobacter pylori is a bacterium that colonizes the gastric and duodenal mucosa and may cause gastritis, peptic ulcer disease, and malignant neoplasms. The infection is transmitted from person to person via close contact and the fecal–oral route.

One of the key virulence factors is the CagA protein, encoded by the cagA gene within the cag pathogenicity island (cag PAI). CagA-positive strains of H. pylori are associated with a stronger inflammatory response in the gastric and duodenal mucosa, significantly increasing the risk of severe complications, including gastritis, peptic ulcer disease, atrophic changes, and malignancies (adenocarcinoma and gastric MALT lymphoma).

IgM antibodies are characteristic of the acute phase of infection: they appear 5–7 days after exposure, peak within 1–4 weeks, and then gradually decline.

Testing for IgM antibodies to CagA is usually performed in combination with other diagnostic methods for H. pylori. Concurrent measurement of IgG antibodies provides a more comprehensive assessment of the immune response. This approach helps clinicians confirm infection, stratify patients according to risk, and make informed decisions regarding eradication therapy.

The test is recommended for patients with clinical symptoms or increased risk of severe outcomes of H. pylori infection:

• chronic gastritis with pronounced inflammatory changes;
• gastric or duodenal peptic ulcer disease;
• gastric MALT lymphoma;
• family history of gastric cancer;
• screening programs for early detection of infection and assessment of complication risk;

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: