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Helicobacter pylori

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Also known as: H. pylori; H-pylori; H. pylori antibody test; H. pylori antigen test; H. pylori breath test; CLO test; Rapid urease test (RUT) for H. pylori
Formal name: Helicobacter pylori

At a Glance

Why Get Tested?

To diagnose an infection with Helicobacter pylori, which can cause peptic ulcers

When to Get Tested?

When you have symptoms of an ulcer, such as gastrointestinal pain, unexplained weight loss, and nausea or vomiting

Sample Required?

A stool sample, blood sample from a vein, tissue biopsy of the stomach lining, or a breath test

Test Preparation Needed?

None for the blood test; there are instructions for the stool and breath tests and biopsy, including avoiding certain medications.

The Test Sample

What is being tested?

These tests are looking for evidence of an infection in the gastrointestinal tract by a bacterium named Helicobacter pylori. This bacterium is known to be a major cause of peptic ulcer disease and is very common, especially in developing countries. It decreases the stomach's ability to produce mucus, making it prone to acid damage and peptic ulcers. H. pylori is also associated with the development of gastric (stomach) cancer.

How is the sample collected for testing?

The sample collected depends on the test ordered. It may be a stool sample to look for the H. pylori antigen or a blood sample drawn from a vein in the arm to detect antibodies to the bacteria.

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. A biopsy can be used to detect other reasons for stomach pain, as well as be cultured or tested in the laboratory for H. pylori. This bacterium produces urease, a special enzyme that allows it to survive in the acidic environment of the stomach. The lab can detect its presence by looking for this enzyme in the tissue sample, or by amplifying DNA fragments to identify H. pylori. The tissue may also be examined under a microscope by a pathologist, who will look for these bacteria or any other signs of disease that may explain a person's symptoms.

Sometimes a breath test, also known as a urea breath test, can be used instead of a biopsy. For this test, the patient drinks a liquid containing a low level of radioactive material that is harmless. If H. pylori is present in the person's gastointestinal tract, the material will be broken down into radioactively-labeled carbon dioxide gas. Alternatively, a nonradioactive natural isotope is ingested by the patient. By testing the expelled air collected from the breath sample, the laboratory can determine if this organism is in the person's body.

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?

No special preparation is needed for the blood test.

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 tissue biopsy, you may be asked to refrain from taking any antibiotics, antacids, or bismuth treatments for 14 days prior to the test.

If undergoing endoscopy, you may be instructed to fast after midnight on the night prior to the procedure.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

National Digestive Diseases Information Clearinghouse. H. pylori and Peptic Ulcer. Available online at through Accessed June 2011.

Michael Selgrad, Arne Kandulski and Peter Malfertheiner. Helicobacter pylori: Diagnosis and Treatment: Diagnosis of Helicobacter pylori. Curr Opin Gastroenterol. 2009;25(6):549-556. Available online at through Accessed June 2011. 

Sources Used in Previous Reviews

The Cleveland Clinic Health Information Center. Breath Test for H. pylori (Online information). Available online at Accessed February 2008.

Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006.

Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology 12th Edition: Mosby Elsevier, St. Louis, MO; 2007.

Chisholm SA, Owen RJ. Application of polymerase chain reaction-based assays for rapid identification and antibiotic resistance screening of Helicobacter pylori in gastric biopsies. Diagn Microbiol Infect Dis. 2008 Jan 11.

Siddique I, et. al Diagnosis of Helicobacter pylori: Improving the Sensitivity of CLOtest by Increasing the Number of Gastric Antral Biopsies. J Clin Gastroenterol. 2008 Apr;42(4):356-360.

Clinical Chemistry: Principles, Procedures, Correlations. Bishop M, Duben-Engelkirk J, Fody E, eds. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2000.

Clinical Chemistry: Theory, Analysis, and Correlations. Kaplan L, Pesce A, eds. 2nd ed. St. Louis: The C. V. Mosby Company; 1989.

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