The Test Sample
What is being tested?
H. pylori is very common, especially in developing countries. The bacteria are present in (colonize) the stomachs and intestines of as many as 50% of the world's population. Most of those affected will never have any symptoms, but the presence of H. pylori increases the risk of developing ulcers (peptic ulcer disease), chronic gastritis, and gastric (stomach) cancer. The bacteria decrease the stomach's ability to produce mucus, making the stomach prone to acid damage and peptic ulcers.
There are several different types of H. pylori testing that can be performed. Some are less invasive than others.
- Stool antigen test – detection of H. pylori in a stool sample
- Urea breath test – detection of labeled carbon dioxide in the breath after drinking a solution
Recommendations for these tests come from published guidelines by the American Gastroenterology Association (AGA), the American College of Gastroenterologists (ACG), and the Infectious Diseases Society of America (IDSA) / the American Society for Microbiology (ASM).
An antibody test using a blood sample is not recommended for routine diagnosis or for evaluation of treatment effectiveness. This test detects antibodies to the bacteria and will not distinguish between a present and previous infection. If the antibody test is negative, then it is unlikely that a person has had an H. pylori infection. If ordered and positive, results should be confirmed using a stool antigen or breath test.
Invasive tests using an endoscopy procedure are less frequently performed than noninvasive tests because they require a tissue biopsy collection. Tests include:
- Histology – examination of tissue under a microscope
- Rapid urease testing – detects urease, an enzyme produced by H. pylori
- Culture – growing H. pylori in/on a nutrient solution
How is the sample collected for testing?
The sample collected depends on the test ordered. For the urea breath test, a breath sample is collected and then the person is given a liquid to drink. Another breath sample is collected at a timed interval. For the stool antigen test, a stool sample is collected in a clean container.
A more invasive test will require a procedure called an endoscopy, which involves putting a thin tube with a tiny camera on the end down the throat into the stomach. This allows for visualization of the stomach lining as well as the ability to take a small piece of tissue (a biopsy) from the lining for examination.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
For the breath test, you may be instructed to refrain from taking certain medications:
- Four weeks before the test, do not take any antibiotics or oral bismuth subsalicylate (Pepto Bismol®).
- Two weeks before the test, do not take any prescription or over-the-counter proton pump inhibitors, such as omeprazole, lansoprazole, or esomeprazole.
- One hour before the test, do not eat or drink anything (including water).
If submitting a stool sample or having a tissue biopsy collected, it may be necessary to refrain from taking any antibiotics, antacids, or bismuth treatments for 14 days prior to the test.
If undergoing endoscopy, fasting after midnight on the night prior to the procedure may be required.