Infection with H. pylori often causes no symptoms at all, but in some individuals it can lead to dyspepsia, ulcers in the stomach or duodenum, or contribute to the development of rare complications such as MALT lymphoma. The infection is much less common in the Western world today, but remains of clinical importance, especially in patients with recurrent upper stomach complaints.
Helicobacter pylori (IgG) is a serological test that measures the presence of antibodies in serum – the fluid that remains after the blood cells and clotting factors have been removed. A positive finding indicates past or ongoing infection, but antibodies may persist long after the bacteria have been eliminated. The test is mainly used as screening or as support in the primary investigation of dyspepsia and ulcer disease.
Immunological background
In infection with H. pylori, the humoral immune system is activated and produces specific IgG antibodies directed against the bacterium's antigens, such as urease, CagA and VacA. These antibodies can be detected in serum using ELISA technology (enzyme-linked immunosorbent assay), which makes it possible to screen for infection in populations where invasive diagnostics are not practical.
The IgG response is part of the body's attempt to limit the infection, but often fails to eliminate the bacterium, which leads to chronic inflammation of the gastric mucosa. It is this long-term inflammation that forms the basis for the development of peptic ulcers, MALT lymphoma and an increased risk of gastric cancer.
Clinical significance
A positive test for Helicobacter pylori (IgG) indicates that you have been exposed to the bacterium. It is particularly useful in the initial investigation of, among other things:
- Dyspeptic symptoms
- Recurrent gastric ulcers
- Familial or previous history of gastric cancer
- Long-term use of NSAIDs in combination with dyspepsia
Since IgG antibodies may persist after eradication therapy, the test is not reliable for assessing treatment response. For follow-up, antigen tests in feces or urea breath tests (UBT), which reflect active infection, are used instead.
Diagnostic strategy for the analysis of Helicobacter pylori
Serology with H. pylori (IgG) is mainly used in primary care and in epidemiological studies. The test does not require fasting, is easy to perform and can be a first step in the diagnosis. In the case of a positive finding in a patient with dyspeptic complaints, eradication treatment with triple therapy (proton pump inhibitor + two antibiotics) is usually recommended.
If symptoms persist despite treatment or if serological findings are negative, further investigation with gastroscopy and biopsies can be considered, especially in patients over 50 years of age or with alarm symptoms such as weight loss, anemia or dysphagia.
Limitations
H. pylori (IgG) is not specific for active infection. A positive test can persist for months or years after the bacterium has been eliminated. However, a negative test practically excludes ongoing infection, since seronegativity usually means that the individual has never been colonized. False positive results can be seen in some individuals with cross-reacting antibodies, and the sensitivity of the test may be lower in older individuals with a compromised immune system.