Type of test : Blood, microscopic examination of antral or duodenal biopsy specimen, breath test, stool

Normal findings

 Blood test

Breath test  : No evidence of H. pylori

Stool test : No evidence of H. pylori

Test explanation and related physiology

H. pylori, a bacterium found in the mucus overlying the gastric mucosa and in the mucosa (cells that line the stomach), is a risk factor for gastric and duodenal ulcers, chronic gastritis, or even ulcerative esophagitis. There are several methods of detecting the presence of this organism. The organism can be cultured from a specimen of mucus obtained through a gastroscope . The organism can also be detected on a gastric mucosal biopsy (from the antrum and greater curvature of the corpus). This is very accurate. The gold standard for diagnosis of H. pylori disease is identifying the infected tissue by Gram, silver, Giemsa, or acridine orange stains.

It often takes several weeks before the results from cultures are available. It is preferable to start treatment before that time on a patient with symptomatic or active ulcer disease. For that reason, rapid urease testing for H. pylori was developed. H. pylori can break down large quantities of urea because of its ability to produce great amounts of an enzyme called urease. In the CLO test, a small piece of gastric mucosa (obtained through gastros copy) is placed onto a specialized testing gel. If H. pylori organ isms are present in the gastric mucosa, the urease (made by the H. pylori) will change the colors of the test material.

A breath test is also available for the detection of H. pylori. In the breath test, radioactive carbon (¹³C) is administered orally. The urea is absorbed through the gastric mucosa, where, if H. pylori is present, the urea will be converted to ¹³CO₂ (where the carbon is radiolabeled). The 13CO₂ is then taken up by the capillaries in the stomach wall and delivered to the lungs. There the ¹³CO₂ is exhaled.

Although H. pylori does not survive in the stool, anti–H. pylori antibody can detect the presence of H. pylori antigen in a fresh stool specimen. Negative results indicate the absence of detectable antigen but do not eliminate the possibility of infection because of H. pylori.

Serologic testing is an inexpensive and noninvasive way of screening and diagnosing H. pylori infection. It is also used as a supportive diagnostic in which no preparation or abstinence from antacids is required. The IgG anti–H. pylori antibody is most commonly used. It becomes elevated 2 months after infection and stays elevated for more than 1 year after treatment. The IgA anti–H. pylori antibody, like IgG, becomes elevated 2 months after infection but decreases 3 to 4 weeks after treatment. The IgM anti–H. pylori antibody is the first to become elevated (about 3-4 weeks after infection) and is not detected 2 to 3 months after treatment. These antibody titers are fast becoming the gold standard for H. pylori detection. These antibodies can be detected with the use of a small amount of blood obtained by finger stick. Serologic testing is often used several months after treatment to document cure of H. pylori infection. Serologic testing is also used to corroborate the findings of other H. pylori testing methods.

Contraindications

 • Patients who are pregnant or are children

• The breath tests use radioactive carbon to which children should not be exposed.

Interfering factors

 • H. pylori can be transmitted by contaminated endoscopic equipment during endoscopic procedures.

* Rapid urease tests can be falsely negative if the patient uses antacid therapy within the week before testing.

Procedure and patient care

 Before

* Explain the procedure to the patient.

* Tell the patient that no fasting is required for the blood test.

• If a biopsy or culture will be obtained by endoscopy, see discussion of esophagogastroduodenoscopy (EGD).

 • If culture is to be performed, be sure that the patient has not had any antibiotic, antacid, or bismuth treatment for 5 to 14 days before the endoscopy.

During

• Collect a venous blood sample according to the protocol of the laboratory performing the test.

• A gastric or duodenal biopsy can be obtained by endoscopy.

 • For the breath test, a dose of radioactive 14C or nonradioactive 13C urea is given by mouth.

After

 • Apply pressure to the venipuncture site.

 • If endoscopy was used to obtain a culture, see procedure for EGD. The specimen should be transported to the laboratory within 30 minutes after collection.

 Abnormal findings

 Increased levels

- Acute and chronic gastritis

 - Duodenal ulcer

- Gastric ulcer

 - Gastric carcinoma

مواضيع ذات صلة

Nucleic Acid –Based Tests

human chorionic gonadotropin (hCG, Pregnancy tests, hCG beta subunit)

homocysteine (Hcy)

HIV serologic and virologic testing

HIV RNA quantification (HIV viral load)

Molecules involved in Lipoprotein metabolism

Lipoproteins

Retinol Binding Protein

Direct Visualization Of The Organism

Direct Detection Methods for Bacillus and Similar Organisms

HIV drug resistance testing (HIV genotype)

herpes simplex (Herpesvirus types 1 and 2, Herpes simplex virus types 1 and 2 [HSV 1, HSV 2], Herpes genitalis)