The 13C-urea breath test (13C-UBT), first described by Graham et al. in 1987, has been proposed as the most important non-invasive method for the detection of Helicobacter pylori infection. For the test, urea marked with the stable carbon isotope 13C is applied orally. If H. pylori’s usually potent enzyme urease is present in the stomach during the test, urea will be hydrolysed to form ammonia and labelled carbon dioxide. The appearance of labelled carbon dioxide in the breath indicates that infection is present. Although 14C can be used for the same purpose, 13C has the advantage of being non-radioactive and can safely be used in children and women of child-bearing age. Many papers describing the methodology of 13C-UBT have been published, but they differ with regard to the dose of 13C-urea, timing of the sample collection, type of test meal used and the equipment required to analyse the breath samples. However, only the dose of 13C-urea and the measuring equipment are directly related to the costs of the test. For reasons of cost efficiency and practicability, the urea dose and measurement duration should be reduced while still maintaining excellent diagnostic accuracy.
Since the original report of 13C-UBT by Graham et al. who used 350 mg of 13C-urea and breath samples collected every 10 min for 3 h, several modifications have been described with regard to the dose of 13C-urea, breath sampling intervals, cut-off values and type of test meal used. These repeated modifications have been used to optimize the simplicity and minimize the costs of the test, as well as to make it applicable on a large scale. The 13C-UBT as described in a standardized European protocol by Logan et al. in 1991, using 100 mg 13C-urea, is an accurate method for the detection of H. pylori infection; however, 75 mg 13C-urea has been shown to be equally effective. Klein et al. validated the protocol with 125 mg 13C-urea, which is currently employed in the USA. In order to render the test less expensive and more convenient, the use of lower doses (38–50 mg) of 13C-urea in gelatine capsules or in citric acid-containing tablets seems to be promising, as it shortens breath sampling intervals to 10–20 min. Enclosing the isotope in a gelatine capsule or in a rapid-releasing tablet shields the urea from exposure to the feeble ureases of oral bacteria that can produce a small early rise in exhaled CO2 tracer. In this way, it is possible to shorten the measurement time to 10 min.
The need to provide a test meal in 13C-UBT has been demonstrated in several studies, as a meal increases the contact time between the tracer and H. pylori urease inside the stomach. Different nutrient meals have been proposed, including fatty test meals, pure orange juice or even full-cream milk. Recently, citric acid, which acts by lowering duodenal pH, and in turn reduces antral motility and relaxes the gastric fundus, has been shown to be an optimal test meal.
It is show that 13C-UBT for the diagnosis of H. pylori infection can be performed using a validated simple methodology with a reduction in urea dose, shortened measurement time and a simple test meal. In a well standardized laboratory, this modification is as accurate as the conventional 13C-UBT for the diagnosis of H. pylori infection.