The urea breath test is a rapid

diagnostic Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine "cause and effect". In systems enginee ...

procedure used to identify

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...

s by ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is thoug ...

'', a spiral

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

implicated in

gastritis Gastritis is inflammation of the lining of the stomach. It may occur as a short episode or may be of a long duration. There may be no symptoms but, when symptoms are present, the most common is upper abdominal pain (see dyspepsia). Other possi ...

gastric ulcer Peptic ulcer disease (PUD) is a break in the inner lining of the stomach, the first part of the small intestine, or sometimes the lower esophagus. An ulcer in the stomach is called a gastric ulcer, while one in the first part of the intestines i ...

, and

peptic ulcer Peptic ulcer disease (PUD) is a break in the inner lining of the stomach, the first part of the small intestine, or sometimes the lower esophagus. An ulcer in the stomach is called a gastric ulcer, while one in the first part of the intestines ...

disease. It is based upon the ability of ''H. pylori'' to convert

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

to ammonia and carbon dioxide. Urea breath tests are recommended in leading society guidelines as a preferred non-invasive choice for detecting ''H. pylori'' before and after treatment.

Principles and mechanism

Patients swallow

labelled with an uncommon

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

, either

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

carbon-14 Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and co ...

or non-radioactive

carbon-13 Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons. As one of the environmental isotopes, it makes up about 1.1% of all natural carbon on Earth. Detection by mass spectrometry A mas ...

. In the subsequent 10–30 minutes, the detection of isotope-labelled

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

in exhaled breath indicates that the urea was split; this indicates that

urease Ureases (), functionally, belong to the superfamily of amidohydrolases and phosphotriesterases. Ureases are found in numerous bacteria, fungi, algae, plants, and some invertebrates, as well as in soils, as a soil enzyme. They are nickel-contai ...

(the

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

that ''H. pylori'' uses to metabolize urea) is present in the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, and hence that ''H. pylori'' bacteria are present. For the two different forms of urea, different instrumentation is required. Carbon-14 is normally measured by scintillation, whereas carbon-13 can be detected by

isotope ratio mass spectrometry Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample. This technique has two different applications in the ea ...

or by mass correlation spectrometry. For each of these methods, a baseline breath sample is required before taking the isotope-labeled urea, for comparison with the post-urea sample, with a 20- to 30-minute duration between them. Samples may be sent to a reference laboratory for analysis. Alternatively, mass correlation spectrometry can be performed as an office-based test since breath samples are continuously collected, and results are provided immediately within minutes. The difference between the pre- and post urea measurements is used to determine infection. This value is compared to a cut-off value. Results below the value are assumed to be negative, those above positive. The cut-off value itself is determined by comparing the results of patients with two or more different detection methods. The value is chosen that gives the best combination of sensitivity and specificity. Both carbon-14 and carbon-13 urea breath tests have high sensitivity and specificity, though the carbon-13 test is preferred in certain populations due to its non-radioactive nature. The test measures active ''H. pylori'' infection. If antibiotics are depressing the amount of ''H. pylori'' present, or the stomach conditions are less acidic than normal, the amount of urease present will be lessened. Accordingly, the test should only be performed 14 days after stopping acid reducing medication (

proton pump inhibitor Proton-pump inhibitors (PPIs) are a class of medications that cause a profound and prolonged reduction of stomach acid production. They do so by irreversibly inhibiting the stomach's H+/K+ ATPase proton pump. They are the most potent inhibitor ...

s, PPI) or 28 days after stopping antibiotic treatment. Some clinicians believe that a reservoir of ''H. pylori'' in dental plaque can affect the result.

References

External links

Typical testing procedure
{{DEFAULTSORT:Urea Breath Test Breath tests Digestive system procedures Helicobacter pylori

Principles and mechanism

See also

References

External links