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  • Also Known As:
  • H. pylori stool antigen
  • H. pylori breath tests
  • Urea breath test
  • CLO test
  • Rapid urease test (RUT) for H. pylori
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At a Glance

Why Get Tested?

To diagnose an infection with Helicobacter pylori (H. pylori), the bacteria that can cause a peptic ulcer, which is a sore on the lining of the stomach, small intestine or esophagus; to determine whether treatment has cured the infection

When To Get Tested?

When you have symptoms of an ulcer, such as ongoing indigestion, gastrointestinal pain that comes and goes, unexplained weight loss, nausea and/or vomiting; about 4-6 weeks after completing treatment for the infection

Sample Required?

A stool sample, a breath sample, or a tissue biopsy of the stomach lining

Test Preparation Needed?

You may need to avoid certain medications; follow any instructions you are given.

What is being tested?

Helicobacter pylori is a type of bacteria that is known to be a major cause of peptic ulcers, which are sores on the lining of the esophagus, stomach or small intestine.  H. pylori testing detects an infection of the digestive tract caused by the bacteria to help diagnose the cause of symptoms and/or ulcers.

H. pylori infections of the digestive tract are very common, with as many as half of the world’s population infected. However, most people with H. pylori never have any symptoms. Still, H. pylori infection increases the risk of developing ulcers (peptic ulcer disease), persistent stomach inflammation (gastritis), and gastric (stomach) cancer. The bacteria decrease the stomach’s ability to produce mucus, making the stomach prone to damage from digestive acid and peptic ulcers.

A few different types of H. pylori testing are available, such as a stool antigen test and a breath test. Some are less invasive than others.

How is the sample collected for testing?

The sample collected depends on the test ordered:

  • For the urea breath test, a health care professional collects an initial sample of your breath by having you breathe into a bag. You are given a liquid to drink containing a substance called urea. Another breath sample is collected after a specific amount of time has elapsed.
  • 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 your health care practitioner to view the stomach lining and take a small piece of tissue (a biopsy) from the lining for examination.

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, usually overnight, may be required. Only water may be permitted.

Common Questions

How is the test used?

H. pylori testing is used to detect the bacteria in the digestive tract, diagnose the infection, and to evaluate whether treatment has cured the infection.

There are several different types of H. pylori testing that can be performed. The following tables summarize these tests:

Without Endoscopy

Stool/fecal antigen test Detects the presence of H. pylori antigen in a stool sample
Urea breath test
  • A health care professional will take an initial sample of your breath (baseline) by having you breathe into a bag.
  • You will be instructed to drink a liquid containing a substance called urea, which is specially ‘labeled’ and then wait about 15 minutes. During this time, if H. pylori is present in your digestive tract, the bacteria will break the urea down into labeled carbon dioxide gas, which is expelled in your breath. (Carbon dioxide is a normal part of the breath that you exhale.)
  • A second breath sample is collected.
  • Both the initial and second sample are sent to a lab for testing. If your second breath sample has a higher level of labeled carbon dioxide than normal, you have H. pylori in your digestive tract.

With Endoscopy: tissue biopsy sample obtained; good tests but ordered less often because invasive

Histology Tissue examined under a microscope by a pathologist, who will look for H. pylori bacteria and any other signs of disease that may explain a person’s symptoms.
Rapid urease testing H. pylori produces urease, an enzyme that allows it to survive in the acidic environment of the stomach. The laboratory test can detect urease in the tissue sample.
Culture The bacteria are grown on/in a nutrient media; results can take several weeks. This test is necessary if the health care practitioner wants to evaluate which antibiotic will likely cure the infection.
PCR (polymerase chain reaction) Fragments of H. pylori DNA are amplified and used to detect the bacteria; primarily used in a research setting.

The stool antigen test and urea breath test are recommended for the diagnosis of an H. pylori infection and for the evaluation of the effectiveness of treatment. These tests are the most frequently performed because they are fast and noninvasive. (The urea breath test is not typically recommended for young children. In children, the preferred test would be the stool antigen test.) Endoscopy-related tests may also be performed to diagnose and evaluate H. pylori but are less frequently performed because they are invasive.

The testing recommendations come from 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).

When is it ordered?

Testing may be ordered when you have pain in your digestive tract and other signs and symptoms of an ulcer. Examples include:

  • Abdominal pain that comes and goes over time
  • Unexplained weight loss
  • Indigestion
  • Feeling of fullness or bloating
  • Nausea
  • Belching

Some people may have more serious signs and symptoms that require immediate medical attention, including sharp, sudden, persistent stomach pain, bloody or black stools, or bloody vomit or vomit that looks like coffee grounds.

H. pylori testing may also be ordered about 4 to 6 weeks after you have finished taking the prescribed antibiotics to confirm that the infection is cured. A follow-up test is not performed on every person, however.

What does the test result mean?

A positive H. pylori stool antigen, breath test, or biopsy indicates that your signs and symptoms are likely caused by a peptic ulcer due to these bacteria. Treatment with a combination of antibiotics and other medications will be prescribed to kill the bacteria and stop the pain and the ulceration.

A negative test result means that it is unlikely that you have an H. pylori infection and your signs and symptoms may be due to another cause. However, if symptoms persist, additional testing may be done, including the more invasive tissue biopsy, to more conclusively rule out infection.

Is there anything else I should know?

People can have digestive tract pain for many reasons; an ulcer caused by H. pylori is only one of them.

If you use antacids within the week prior to testing, the rapid urease test may be falsely negative. Antimicrobials, proton pump inhibitors, and bismuth preparations may interfere with test results.

What is the treatment of peptic ulcer caused by H. pylori?

Treatment usually involves a combination of antibiotics and drugs to reduce the amount of stomach acid produced, such as proton pump inhibitors and histamine receptor blockers, as well as a bismuth preparation, such as Pepto-Bismol®, taken for several weeks.

Does everyone with H. pylori get ulcers?

No, many people have evidence of infection but have no symptoms of ulcerative disease. The reason why some people with H. pylori infections develop peptic ulcers and others do not is not yet understood.

Should everyone be tested for H. pylori?

Since the infection is very common and most people do not ever get ulcers, testing is generally only recommended for those who have signs and symptoms.

How did I get infected with H. pylori?

The bacteria are believed to be transmitted by eating food or drinking water that has been contaminated with human stool, or possibly through contact with the stool, vomit, or saliva of an infected person. Exposure to family members with H. pylori seems to be the most likely opportunity for transmission.

Does everyone treated for H. pylori get better?

The majority of people who successfully complete the combination antibiotic therapy get rid of these bacteria from their digestive tract. However, resistance to some of the antibiotics may occur and, therefore, the bacteria may continue to multiply despite appropriate therapy.

If I am treated and the infection goes away, can I get another H. pylori infection?

Treatment does not make a person immune, so there is always the potential for becoming infected again.

Why is the blood test for H. pylori antibodies no longer recommended?

The American Gastroenterology Association, the American College of Gastroenterologists, the Infectious Diseases Society of America and the American Society for Microbiology do not recommend the antibody blood test for routine use in diagnosing an H. pylori infection or evaluating its treatment as the test cannot distinguish between a present and previous infection. A few healthcare practitioners still order this test, but many laboratories have stopped offering it. If performed and the blood test is negative, then it is unlikely that the person has had an H. pylori infection. If it is positive, then the presence of a current H. pylori infection should be confirmed with a stool antigen or breath test.

View Sources

Sources Used in Current Review

Santacroce, L. and Bhutani, M. (2018 August 9, Updated). Helicobacter Pylori Infection. Medscape Gastroenterology. Available online at https://emedicine.medscape.com/article/176938-overview. Accessed on 9/08/18.

Lai, S. (2017 August 1, Updated). Tests for H. pylori. MedlinePlus Medical Encyclopedia. Available online at https://medlineplus.gov/ency/article/007501.htm. Accessed on 9/08/18.

Couturier, M. and Jarboe, E. (2018 August, Updated). Helicobacter pylori. ARUP Consult. Available online at https://arupconsult.com/content/helicobacter-pylori. Accessed on 9/08/18.

Zingman, B. et. al. (2017 October 12, Updated). Helicobacter pylori infection. MedlinePlus Medical Encyclopedia. Available online at https://medlineplus.gov/ency/article/007715.htm. Accessed on 9/08/18.

(© 1995– 2018). Helicobacter pylori Breath Test. Mayo Clinic Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81590. Accessed on 9/08/18.

(© 1995– 2018). Helicobacter pylori Antigen, Feces. Mayo Clinic Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81806. Accessed on 9/08/18.

Sultan, M. et. al. (2018 February 12, Updated). Pediatric Helicobacter Pylori Infection. Medscape Pediatrics: General Medicine. Available online at https://emedicine.medscape.com/article/929452-overview. Accessed on 9/08/18.

(April 5, 2017) Armand W. H. pylori, a true stomach “bug”: Who should doctors test and treat? Harvard Health. Available online at https://www.health.harvard.edu/blog/h-pylori-a-true-stomach-bug-who-should-doctors-test-and-treat-2017040511328. Accessed Sep 2018.

(© 1995–2018). Helicobacter pylori Diagnostic Algorithm. Mayo Clinic Mayo Medical Laboratories. Available online at https://www.mayocliniclabs.com/it-mmfiles/Helicobacter_pylori_Diagnostic_Algorithm.pdf. Accessed Sep 2018.

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Sources Used in Previous Reviews

The Cleveland Clinic Health Information Center. Breath Test for H. pylori (Online information). Available online at http://www.clevelandclinic.org/health/. 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.

National Digestive Diseases Information Clearinghouse. H. pylori and Peptic Ulcer. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/hpylori/. 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 http://www.medscape.com/viewarticle/711405_2. Accessed June 2011.

Baumann, A. and Katz, P. (Updated 2014 January 27). Helicobacter Pylori Antigen Test. Medscape Drugs & Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/2117821-overview. Accessed October 2014.

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Longstreth, G.(Updated 2013 August 22). Tests for H pylori. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/007501.htm. Accessed October 2014.

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Kelly, J. (2014 September 30). WHO Urges H pylori Screening to Prevent Gastric Cancer. Medscape News [On-line information]. Available online at http://www.medscape.com/viewarticle/832581. Accessed October 2014.

Baron, E. et. al. (2013 July 10). A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2013 Recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM). [On-line information]. Available online through http://www.idsociety.org. Accessed October 2014.

Pagana, K. D., Pagana, T. J., and Pagana, T. N. (© 2015). Mosby’s Diagnostic & Laboratory Test Reference 12th Edition: Mosby, Inc., Saint Louis, MO. Pp 494-496.

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