The urease test The breath test is a specific test to indirectly detect the presence of Helicobacter pylori in the gastric mucosa. This microorganism is characterized by being a strong producer of urease, therefore this test has a great sensitivity.
In addition, the test is considered to be highly specific because the Helicobacter pylori it is so far the only known bacteria that can lodge, survive and cause pathology in the gastric mucosa.
On the other hand, urease is not an enzyme that can be found in the stomach physiologically or for different causes. So if the breath or urease test is positive there is no doubt that the H. pylori is present.
Taking into account that the Helicobacter pylori has a high prevalence in the world population and represents a risk factor for gastric cancer, it is important that an early diagnosis is made.
For this, there are various diagnostic methods that detect the presence of Helicobacter pylori, some are invasive and some are non-invasive.
There is no doubt that gastric mucosa biopsy is one of the most reliable techniques, but its disadvantage is that it is an invasive technique, making it difficult to perform. Also, it only tests a small portion of the total stomach..
On the other hand, it must be considered that this infection usually begins in childhood and therefore it is necessary that there are non-invasive diagnostic techniques. Among the non-invasive techniques with great specificity and sensitivity are the urease test or breath test.
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This technique is an indirect method to diagnose the presence of Helicobacter pylori. This is based on the detection of urease production by the microorganism. For this, the patient is given a dose of urea labeled with C14.
If the microorganism is present it will rapidly degrade urea to ammonia and CO.two. The COtwo generated passes into the blood and from there to the lungs, being eliminated by respiration (exhaled air). The breath test is based on collecting that exhaled air and detecting or measuring radioactivity.
If radioactivity is detected, the urease test for Helicobacter pylori is positive. This technique has 97 - 100% sensitivity and specificity.
To perform this test, the patient must prepare 2 weeks to 4 weeks in advance and must meet certain requirements:
-The patient must not have been under antibiotic treatment for at least 1 month prior to the study.
-On the other hand, the patient may not have been or be under treatment with certain medications, such as: proton pump inhibitors (gastric protectors), medications containing bismuth or sucralfate. The presence of these drugs provides false negatives.
-The day of the test you must go completely fasting.
The patient is given a 1 mg 14C-labeled urea capsule with 20 ml of water. It can also be performed with C13-labeled urea, but the procedure is more complicated and expensive. For this reason, the most widely used is the C14 isotope..
When ingesting the capsule the patient should avoid touching the lips or cheeks. After 3 minutes the patient should ingest 20 ml more of water.
From this moment they wait 7 minutes. Once the time has elapsed, the patient is asked to exhale air through the mouth through a hollow cannula, the opposite end of which will be immersed in 2.5 ml of breath container liquid..
This liquid is blue in color and is designed to become crystalline when it receives 2 mmol of carbon dioxide. The next step consists of adding 10 ml of the scintillation liquid, mix it and leave it to rest for 1 hour..
It is then taken to specialized equipment called a beta scintillation counter. Finally, to calculate the disintegration per minute the following formula is used:
The procedure is similar but has some changes. In this case, two breath samples should be taken, one at the beginning and another after 20 minutes of having consumed the urea labeled with C13..
The samples are passed through an apparatus that detects the concentration of C13 by colorimetry. The measuring instrument is called a spectrophotometer.
A low baseline C13 value with a significant increase in C13 in the second sample demonstrates a positive result..
Gastric infection by Helicobacter pylori reaches alarming figures worldwide; statistics express that almost 50% of the population may be infected by this bacterium.
Helicobacter pylori causes chronic gastritis and peptic ulcers. In addition, there are studies that show that this bacterium is a risk factor for the subsequent suffering of gastric cancer in a proportion of 2-6%. These figures are important, since it is known that this neoplasm is the second oncological pathology that causes more deaths worldwide.
It should be noted that people are susceptible to being infected with this bacterium from an early age. Due to all this, it is important to have diagnostic methods that are easy to use, accessible and at the same time highly sensitive and specific..
Gastric mucosa biopsy, together with rapid urease test, has long been considered the “Gold Standard” tests for the detection of Helicobacter pylori, but they have the disadvantage that both are invasive tests.
In this sense, Aguilar et al. Demonstrated that the urease test or breath test offers results comparable to those obtained with the gastric biopsy and the rapid urease test. In addition, it also serves to evaluate the follow-up of treatment.
That is why some countries use the breath test as a routine test for the diagnosis of this bacterium. Although it should be noted that the breath test is not the only option, there are other non-invasive, inexpensive and reliable methods that are also useful, such as the detection of antigen of H. pylori in feces.
Serology, on the other hand, despite being useful, is not good for monitoring.
-Method with high sensitivity and specificity
-Non invasive
-Easy to perform in the case of using C14 isotope
-Economical if done with C14 isotope.
-The C13 isotope is not radioactive and is suitable for children and pregnant women.
-Evaluate the entire stomach.
-The method that uses the C14 isotope cannot be used in pregnant women and children because it is radioactive. In these cases it is preferable to use the C13 isotope, however the latter has the disadvantage that the technique is more laborious and expensive.
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