H. pylori Test

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H. pylori test

Definition

H. pylori tests are used in gastroenterology to detect the presence of the Helicobacter pylori bacterium that causes peptic ulcer disease. H. pylori is a Gram-negative, motile, microaerophilic bacteria so named because of its spiral shape.

Purpose

H. pyloriinfection of the mucosal lining of the duodenum is a known cause of duodenal ulcers. H. pylori is also strongly implicated in other gastric conditions, including acute and chronic gastritis , gastric ulcers, stomach cancer , and lymphoma associated with the lymphoid tissues of the gastrointestinal mucosa.

There are different kinds of H. pylori tests, but they all have the same purpose: to determine if a person has the H. pylori bacteria in his or her gastrointestinal tract. After a patient has been diagnosed with a peptic ulcer disease, the gastroenterologist usually tests for the bacteria and, if it is present, treats it with a combination of two antibiotics . Following treatment the patient may be tested again to determine that the treatment was successful.

H. pylori may be diagnosed from tests performed on endoscopic biopsy specimens from the stomach or duodenal mucosa, breath analysis, tests on plasma or serum for specific antibodies, or tests on stool for H. pylori antigens.

ENDOSCOPIC BIOPSY. A culture can be done on tissue obtained by biopsy, but is generally not performed because recovery of organisms is variable. Biopsy specimens taken from the stomach or duodenum may also be examined for Gram-negative spiral rods indicative of infection, but more often are tested for H. pylori by adding a sample of the tissue to a broth containing urea. The bacterium produces urease, which hydrolyses the urea and forms carbon dioxide and ammonia. The ammonia increases the pH of the medium causing the pH indicator to turn red.

BREATH TESTS. These tests are based on detection of carbon dioxide gas produced from the hydrolysis of urea. Breath tests are non-invasive and highly accurate in determining if the bacterium is present. They are often used when an endoscopy is contraindicated and to follow-up antibiotic treatment. The patient is given an oral dose of urea labeled with radioactive carbon. The carbon is carried to the lungs by the blood . The patients exhales into a vial and the radioactivity of the expelled air in the vial is measured. A nonradioisotopic breath test is also available.

SEROLOGICAL TESTS FOR ANTIBODIES TO H. PYLORI. ELISA (enzyme-linked immunosorbent assay) and other immunoassay methods are available for IgG, IgA, and IgM antibodies to H. pylori. The IgM test detects antibodies formed two to four weeks after infection. IgG and IgA tests require up to two months after infection before becoming positive. These tests are accurate and reliable screening tests for exposure to H. pylori. However, antibodies persist after successful treatment. For this reason, the breath test is preferred after treatment to identify drug resistant cases.

Precautions

Endoscopy may be contraindicated by a history of gastrointestinal (GI) bleeding, recent GI surgery, and diverticula in the esophagus. Breath testing using a radioisotopic preparation is contraindicated in pregnancy . The breath test may be negative if the patient is receiving antibiotic therapy and certain medications.

Preparation

Endoscopy is an invasive procedure, and is performed in a hospital or clinic usually on an outpatient basis. Overnight fasting is required. To reduce the discomfort

KEY TERMS

Endoscope —A thin, lighted tube with a tiny camera attached to the end. It allows the doctor to see the lining of the esophagus, stomach, and duodenum.

Endoscopy —A procedure that uses an endoscope.

Gastroenterology —The study of the digestive system and diseases and disorders affecting it.

Invasive procedure —A medical procedure that requires entrance of a foreign object into the human body.

Non-invasive procedure —A medical procedure that does not require entrance of a foreign object into the human body.

Serology —Blood tests.

Urea —A waste product of the breakdown of proteins.

associated with the procedure, the patient is mildly sedated and a topical anesthetic is sprayed in the throat. Vital signs and history are important to insure that the patient does not have a condition that contraindicates the procedure. An intravenous line is used to instill fluids and the sedative.

For the breath test, a dose of radiolabeled urea is given orally to the patient. For serological tests, venipuncture is performed using standard precautions for prevention of exposure to bloodborne pathogens.

Aftercare

Following endoscopy, patients should be observed while recovering from sedating medications for any signs of GI bleeding or pain and treated accordingly. The patient should remain under medical supervision until fully alert. After venipuncture, hemostasis should be accomplished by applying direct pressure to the puncture site.

Complications

Endoscopy may be associated with GI bleeding, allergic reaction to medications, and throat or abdominal pain. Rare complications also include perforation of an upper GI organ, aspiration of gastric fluid, and phlebitis. Breath and serological tests are not associated with significant complications.

Health care team roles

Endoscopy is performed by a gastroenterologist with the assistance of registered nurses. Breath testing can be administered by a physician or nurse. Venipuncture is performed by a physician, nurse or phlebotomist. Serological testing is performed by a clinical laboratory scientist, CLS(NCA)/medical technologist, MT(ASCP) or clinical laboratory technician, CLT(NCA)/medical laboratory technician, MLT(ASCP).

Resources

PERIODICALS

Fallone Carlo A., Sander J.O. Veldhuyzen van Zanten, Naoki Chiba. "The Urea Breath Test for Helicobacter pylori Infection: Taking the Wind Out of the Sails of Endoscopy." Canadian Medical Association Journal (February 8, 2000): 371-2.

Sutton, Fred M. "Diagnosis of H. pylori Infection." Infectious Medicine 15 no. 5 (1998): 331-336.

Veldhuyzen van Zanten, Sander J. O. "Treating Non-Ulcer dyspepsia and H. pylori: It Is Economically and Clinically Sensible But It Won't Make Most Patients Better." British Medical Journal (September 16, 2000).