Helicobacter pylori may be diagnosed by several invasive or noninvasive Tests:
- Histologic examination of gastric mucosa: Organisms stain poorly with H&E but may be demonstrated with Giemsa or silver staining.
- The culture of gastric mucosa: Special culture techniques are required for isolation. The organism is microaerophilic and capnophilic and yields growth within 5 days on enriched media.
- Urease activity (direct tissue or Urease breath test): Strongly positive.
- Specific antigen: A commercially available assay for detection of H. pylori antigen in faeces shows a sensitivity of approximately 90% and specificity of approximately 95% for detection of active infection. Helicobacter pylori antigen may be useful for monitoring response to therapy.
- Serology: Helicobacter pylori antibody IgG is typically measured. Positive response is predictive of active infection in patient populations where the prevalence of active infection is not high. Antibody levels may remain persistently positive for a period after successful therapy, so serology may have a limited role in an early test of cure.
Ammonia is derived mostly from protein degradation. Most of the ammonia in the blood comes from the intestine, where colonic bacteria use ureases to break down urea to ammonia and CO2. Eight-five percent of blood from the intestine is carried directly to the liver via the portal vein and 85% of ammonia is converted back to urea and excreted by the kidneys and colon. Helicobacter pylori in the stomach appear to be an important source of ammonia in patients with cirrhosis.
Normal range: <50 μmol/L.
The Urease breath test
The urea breath test (UBT) allows a non-invasive diagnosis of infection by Helicobacter pylori. The bacterial toxins weaken the stomach protective mucus allowing the stomach cells to be susceptible to the damaging effects of acid and pepsin. It has been discovered that the bacterium produces urease, an enzyme that makes it possible to dissociate the urea molecule (N2H4CO) into ammonia (NR|OH) and carbon dioxide (CCh), so the presence of the bacterium can be revealed by detecting the enzymatic activity of urease. The urease enzymatic activity can be assessed by measuring the chemical conversion of urea to carbon dioxide in a breath test.
urea breath test procedure & Instructions
The 13 OR 14 C-urea breath test ( 13 C-UBT) requires the patient to swallow an isotopically labelled ( 13 C OR 14C) urea tablet. The urea is subsequently hydrolyzed to ammonia and labelled CO 2 by the presence of H. pylori urease activity. After approximately 30 minutes, an exhaled breath sample is collected, and 13 CO 2 levels are assessed using isotope ratio mass spectrometry. An increase of more than 5% in the I3C breath content is considered as the definite sign of the Helicobacter Pylori infection .
urea breath test normal range
A value of <3/5 is taken as normal, the value of the isotopic ratio may be determined to detect a defined absorbing line for each one of the two isotopes and to calculate the ratio between the respective intensities. The natural isotopic content of the I3C isotope in the breath is 1.095% of the total CCh, and very low amounts of I3C are involved in increasing the isotopic ratio of 5%. The precision reached by TOLAS is sufficient to perform the analysis.
urea breath tests results
Negative: <5 0 disintegrations per minute (DPM) for H. pylori
5 0–199 DPM indeterminate for H. pylori
>2 00 DPM positive for H. pylori
A sensitive analysis of trace gases in the exhaled breath is possible through the high-resolution molecular Spectroscopy based on tunable diode laser (TOLAS). An exemplary application of TDLAS in gastroenterology is the diagnosis of the Helicobacter pylori infection through the urea breath test based on the measurement of the i3CO2/12CO2 isotopic ratio in the exhaled breath.
urea breath tests cost
Estimated costs of the urea breath test is between 50 – 80 $