How does the breath test work?

Breath test principles are very simple. Patient takes orally the preparation labelled with carbon-13 stable isotope. In the case of H.pilory detection one should take ¹³C-urea, if it is necessary to obtain the hepatic integral function he takes ¹³C-amonipyrine, etc. To garantee the patient total safety all preparations are labelled with non-radioactive carbon-13 stable isotope. In the body the preparation is metabolized and decomposes partially or totally after which it's removed. During the exchange reactions the carbon is oxidized and removed from the body by lungs in the form of carbon dioxide.

Utilizing of isotope label in diagnostic preparation brings to breath 13С/12С isotope ratio change which can be detected by means of special equipment. The value of isotope ratio change defines the preparation metabolizm rate and as a consequence the presence or absence of the specific disease.

If the bacterium Helicobacter pylori is diagnosed the patient takes orally the ¹³C-urea solution. Test is based on the ability of urease (an enzyme excreted by the bacterium) to hydrolize urea into ammonia and carbon dioxide.

If the patient is infected by H. pylori 13C-urea will be hydrolized at the stomath, otherwise it will be absorbed and withdrawn with the natural urea in practically unchangeable state (Т_1/2 = 2,5 ч). Bicarbonate H¹³CO₃ formed at 13C-urea decomposition is absorbed by gastric walls, enters into a blood flow and then is withdrawn out of the organism as ¹³CO₂ through the lungs. The hydrolysis second component is ammonia NH₃. It's turned into ammonium ion NH₄⁺, absorbed, metabolized and withdrawn by kidneys. As urea is labelled by carbon-13 stable isotope and in the case of H.pilori infection it hyrolizes with ¹³CO₂ formation the isotope composition change in exhaled carbon dioxide can be recorded.

If a patient is not infected with H. pylori then urea hydrolysis doesn't take place and isotope composition will be similar to natural.