The least invasive procedure to diagnose active H. pylori infection after giving treatment
|A||Urease study of gastric biopsy specimen|
|B||Urea breath test with C14|
|C||Urea breath test with Cl3|
Urea Breath Test
a. Another noninvasive test used for diagnosing H. pylori is the carbon-labeled urea breath test.
c. The test is performed by having the patient ingest a carbon isotope–labeled urea using either 14C or 13C. If 13C is used, mass spectrometry is required, whereas it is not required for 14C, but 14C is associated with a low level of radiation exposure.
d. After ingestion of the carbon isotope, urea will be metabolized to ammonia and labeled bicarbonate if H. pylori infection is present.
e. The labeled bicarbonate is excreted in the breath as labeled carbon dioxide, which is then quantified.
f. The urea breath test is less expensive than endoscopy and samples the entire stomach.
g. False-negative results can occur if the test is done too soon after treatment, so it is usually best to test 4 weeks after therapy is finished.
h. The urea breath test is the method of choice to document eradication.
Rapid Urease Assay
a. The method of choice to diagnosis H. pylori if endoscopy is employed is the rapid urease test. This is another test based on the ability of H. pylori to hydrolyze urea.
b. The enzyme urease catalyzes degradation of urea to ammonia and bicarbonate, creating an alkaline environment that can be detected by a pH indicator.
c. Consequently, endoscopy is performed and gastric mucosal tissue biopsied.
d. Mucosal biopsy samples are placed into a liquid or solid medium containing urea and a pH indicator.
e. Sensitivity is about 90% and specificity 98%, and the results are available within hours.
a. Endoscopy can also be performed with biopsy samples of gastric mucosa followed by histologic visualization of H. pylori.
b. H. pylori is identified by its appearance and colonization sites with routine hematoxylin and eosin stains or with special stains such as silver, Giemsa, or Genta, for improved visibility.
c. Sensitivity is about 95% and specificity 99%.
d. This test is widely available and affords the clinician the ability to assess the severity of gastritis as well as to confirm the presence or absence of the organi