Helicobacter pylori antigen (stool)

H. pylori commonly colonises the gastric mucosa. Is examined alongside other findings with chronic gastritis and gastric ulcers. The stool antigen test, like the breath test, is regarded as a reliable non-invasive way of detecting active colonisation.

What the Helicobacter pylori stool antigen test shows

Together with shed stomach lining, Helicobacter bacteria and their fragments also reach the gut and are excreted in the stool. The test detects certain proteins of the bacterium (antigens) using highly specific, so-called monoclonal antibodies. It therefore shows whether the germ is living in the stomach at the time of sampling. In this it differs from the antibody test in the blood: antibodies remain detectable long after the germ has disappeared and therefore cannot distinguish between past and current colonisation.

What influences the result of the Helicobacter antigen test?

The result depends on how many bacteria are currently living in the stomach. Acid-suppressing drugs of the proton pump inhibitor type, antibiotics and bismuth preparations can temporarily reduce the bacterial load so far that the test is negative even though the germ is still present; the bacteria also retreat to higher sections of the stomach. Very watery diarrhoea can dilute the antigen in the stool, too, and bleeding in the upper digestive tract can interfere with the measurement. Because the test only detects the antigen, it says nothing about how strongly the stomach lining is inflamed.

Positive Helicobacter pylori antigen – what is happening in the stomach?

A positive result shows that Helicobacter pylori is currently colonising the stomach lining. Colonisation is practically always accompanied by inflammation of the lining, although this usually goes unnoticed. Whether complaints arise depends, among other things, on the bacterial strain, on where in the stomach the inflammation sits and on acid production. If the test is negative after previously detected colonisation, the germ is no longer detectable at the time of sampling – the antibodies in the blood may nevertheless still be positive.

The interpretation is given in your report.