Urea Breath Tests - general information
Helicobacter pylori is a gram negative microaerophilic curved bacillus with an affinity for human gastric mucosa.
The organism is prevalent in up to 54% of the population in developed countries such as Australia. Acquisition occurs with age at a rate of 0.5-1% per year. Studies have shown it to be present in up to 100% of patients with duodenal and gastric ulceration, up to 94% of patients with gastric cancer, 92% with gastric lymphoma and 92% of patients with active chronic gastritis. It has been associated with non-ulcer dyspepsia.
Eradication of the organism leads to the disappearance of gastritis and has been shown to significantly reduce the relapse rate of duodenal ulcer disease. The one year relapse rate for duodenal ulcer treated with conventional acid suppression, is as high as 80% but can be reduced to almost zero with successful eradication of the organism, thus modifying the natural history of the disease.
Regression of low grade gastric MALT lymphoma has been shown with H. pylori eradication. In gastric carcinoma, epidemiological studies have identified a link between the organism and the development of cancer. The organism has been shown in some studies to increase gastric epithelial cell proliferation which may then be associated with an increased risk of carcinoma but the details of the exact pathogenic mechanism are unclear.
Diagnostic tests for H. pylori
Can be performed on biopsies obtained at upper Gastro
Intestinal endoscopy, and are evaluated by :
- histology and phase contrast microscopy
- culture
- rapid urease test (CLO test)
Non-invasive tests include :
- serological tests - agglutination tests, complement fixation tests or enzyme linked immunoassay - will show if the patient has had an infection
- 14C or 13C urea breath test - diagnoses active infection
Principles of Urea Breath Testing
Subjects are given urea labelled with 14C or 13C orally.
- H. pylori produces copious amounts of urease which breaks down (hydrolyses) the labelled urea to produce labelled CO2 and ammonia.
- CO2 is dissolved in the blood stream and transported to the lungs for removal.
- Exhaled CO2 is trapped, processed and analysed.
- 14C is a beta emitting radioisotope and can be detected using liquid scintillation counting
- 13C is a stable, non-radioactive isotope that is measured using a mass spectrometer
Indications for Urea Breath Testing
- To confirm Helicobacter pylori colonisation
- To monitor the success of eradication of H. pylori in patients with peptic ulcer, where the testing is performed at least one month after the completion of eradication treatment.
A Medicare benefit (item 12533) is payable if the patient is referred by another medical practitioner.
