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Respiratory test for Helicobacter pylori: how to prepare, how to be carried out, decoding, norm
Last reviewed: 19.10.2021
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Many researchers question the fundamental role of Helicobacter pylori in the pathogenesis of gastritis and peptic ulcer, believing that the active multiplication of these bacteria begins on an already damaged pyloroduodenal mucosa. However, an undeniable fact is the detection of Helicobacteriosis in almost 90% of patients with ulcers and chronic gastritis. Moreover, eradication of this bacterium promotes rapid regression of peptic ulcer and provides a long period of remission in patients with ulcerative lesions of the stomach and duodenum. Diagnosis of the presence of infection can be different methods - to examine fingerprints and biopsies of the mucosa, taken by the endoscopic method, to determine the presence of antibodies in the blood to Helicobacter Pylori or antegen in the feces. A safe and very effective diagnostic method is the Helicobacter pylori breath test, which uses its ability to produce a hydrolytic urease catalyst that accelerates the cleavage of urea into ammonia and carbon dioxide. Testing consists in conducting a comparative analysis of two samples of exhaled air. The first is taken before taking a solution of carbamide with a normal isotopic composition or with a labeled carbon atom C13, the second after it. This study is quite informative and answers the question of the presence of Helicobacter pylor bacteria in the patient and the degree of their activity.
The recent comparisons of the efficacy of different methods for studying Helicobacter infection show the greatest number of positive results, especially when performing a breath test, even in comparison with a microscopic analysis of the biopsy. Experts explain the negative result of histology or polymerase chain reaction with positive results of the urease test by the complexity of culturing the microorganism and the absence of bacteria in the taken random samples. After all, when testing exhaled air, the products of vital activity are determined, and not the presence of microorganisms themselves, which are simply absent from a randomly selected biomaterial.
[Indications for the procedure of the respiratory test for Helicobacter pylori
Patients with established diagnosis of inflammation or peptic ulcer of the digestive tract organs - esophagus, stomach and / or duodenum, with recurrences of helikobacteriosis in the anamnesis, members of the infected family are subject to testing.
Pain in epigastrium, abdominal discomfort, dyspeptic disorders - such symptoms are also grounds for referring the patient to a urease respiratory test.
Thus, both the primary diagnosis of Helicobacter pylori infection and the control one are performed after the treatment.
Information on where to make a respiratory urease test for Helicobacter should be owned by the attending physician giving direction for the examination. Unfortunately, district hospitals and rural dispensaries, as well as non-specialized medical institutions, as a rule, are not equipped with the necessary equipment for carrying out a urease test. Commercial laboratories and specialized gastroenterological clinics, in capitals and large cities, have equipment for carrying out a respiratory test for Helicobacter infection. The speed of the analysis and its accuracy depend on the equipment of the laboratory.
Preparation
In order to ensure that the test results are as informative and reliable as possible, the patient must adhere to a set of recommendations for preparation. This analysis of exhaled air is carried out in the morning on an empty stomach. On the eve, until ten o'clock in the evening, it is allowed to eat an easily digestible supper.
The day before the scheduled study, you do not need to include legumes (soy, peas, beans, etc.) in the diet.
Before the test for a month and a half, it is necessary to stop taking antibacterial and secretion-reducing drugs.
Analgesics, anti-inflammatory and antacids do not take five days during the previous test, and alcohol-containing drinks and tinctures - for three.
For three hours before the test, do not smoke and do not use chewing gum.
Going to be tested, conscientiously brush your teeth and rinse your mouth.
Who to contact?
Technique of the respiratory test for Helicobacter pylori
Attention: during the study the patient should control his salivation. At occurrence of a dyscomfort, a respiratory tube take out from a mouth, swallow a saliva, and continue the test. The presence of saliva in the respiratory tube should be completely ruled out, since in this case the test results are recognized as invalid and the procedure is to be repeated in about an hour.
The patient puts a plastic tube of the expiratory air analyzer deep enough in his mouth and breathes through it in the usual rhythm several times.
Then the tube is removed and the patient is given a urea solution (100 g of carbamide per 50 ml of water). After that, the patient continues to breathe through the tube, without straining, with the usual intensity. After the expiration of the time required for the test, the analyzer is given to the doctor who performs the diagnostics, the result becomes known within a few minutes. Diagnostic systems Helik are produced with an indicator tube (the test is performed for a quarter of an hour), the more modern is a digital model where the test result appears on a computer monitor (it takes nine minutes to complete). The procedure is controlled by a doctor. A test with a stable 13C carbon isotope as the reacting component is considered to be the most accurate.
Another method of diagnosis is the determination in the exhalation of the loading level of ammonia vapors. The technique is similar, the reagent is cheaper (urea is a normal isotope composition). Its accuracy is estimated as lower. However, it is also quite informative (about 85%).
Of all the diagnostic methods of 13C, the urease respiratory test for Helicobacter has a number of undeniable advantages. It is performed without damaging the skin surface and penetrating through the natural openings of the body, so even minimal injuries during manipulation are excluded. In addition, it is characterized by high specificity and sensitivity (manufacturers estimate these values above 83%), and also - 95-100% accuracy.
If the analysis for the concentration of carbon isotopes C13 in this laboratory is done with an infrared (laser) mass spectrometer, samples of the patient's exhaled air in a hermetically packaged container are transported to a laboratory equipped with this equipment (sometimes even abroad). The analysis is done within 24 hours, however the samples of exhalations are stored up to 10 days.
Clinicians put the analysis of exhaled air in first place among the methods of primary diagnosis of Helicobacter pylori infection and control of the effectiveness of treatment. More precise is the only cytological study of a biopsy specimen taken with endoscopy. But this rather traumatic method is not recommended for all patients, at the same time, a urease respiratory test can be performed even for pregnant women and children. The isotope of carbon 13C, which is marked with a carbamide solution, is natural for the human body. This stable non-radioactive isotope makes up slightly more than 1% of the total amount of carbon in the person's exhaled air, its remaining part is in the form of 12C. The presence of infection and the ureaase cleavage reaction of carbamide urease, produced by microorganisms, allows the hydrolysis process to be started quickly. Carbon dioxide containing a labeled atom is absorbed into the blood and leaves the body with the exhalations of the patient. In infrared light, samples of expiration are studied before and after carbamide consumption, by analyzing with a mass spectrometer or a rapid Helicopter test. By the ratio of the form of carbon C13 to C12, a conclusion is made about the presence of infection and the degree of its severity. High accuracy in the range of 95-100% and more gives the first version of the study, but such equipment is not available in any laboratory. And a long process of transportation to equipment equipped with a mass spectrometer can distort the results of the analysis.
A quick Helicopter test has a lower sensitivity (about 80-85%), but it is simple and more affordable. It can be performed in any medical institution, since the equipment is portable. The reagent for the solution is a solution of ammonia or carbon isotope 13C.
Normal performance
In a healthy person, the test result should be negative. If the content of 13C carbon isotope in the air exhaled by the patient does not exceed one ppm (‰) is the norm of the Helicobacter breath test. The difference in the results between the first stage (before carbamide intake) and the second (after intake) should be zero or be a negative number. The graph shows the constant value of the reagent content relative to the basal level.
A positive result is considered to be more than 1 ‰ of the 13C isotope in exhalation, with four degrees of severity of Helicobacter pylori infection. The norm of the rapid Helicopter test is the absence of a difference between the indices preceding the reception of the solution and in the second stage after its use. In Helicobacter-Positive Patient, the difference exceeds the zero value, and the graph on the y-axis shows a pronounced increase in the reagent in the exhaled air.
The value of 1.5-3.4 ‰ is interpreted as the presence of traces of bacteria, corresponds to the lightest degree of seeding. Bacteria are inactive, you can recover quickly.
A low threshold corresponds to a seeding level of 3.5-5.4 ‰, as a small one is treated with an indicator of 5.5-6.9 ‰.
The active phase of propagation of the pathogen corresponds to values of 7-14.9 ‰. At this stage more severe treatment is predicted, corresponding to a severe degree of infection.
An extremely severe degree corresponds to a level of seeding of 15 ‰ and higher. Treatment will be persistent and long-lasting, however, provided that the patient faithfully follows all medical recommendations, the elimination of Helicobacter pylori colonies is possible even in this case.
The result obtained after the study on an infrared (laser) mass spectrometer is also determined as the comparative content of carbon isotopes C13 bas in the first expiration sample of the patient with the C13 cont sample after taking the solution. The difference of these parameters is analyzed. Negative results are not more than 0,3 ‰ (border value), if it is exceeded, the test is considered positive. Massiveness of seeding is directly proportional to the value of the indicator.
The device for analysis
Expression tests of exhaled air are more common in the territory of the post-Soviet space. They are made on site and do not require transportation and storage of samples. The device for rapid analysis can be equipped with indicator tubes - with a normal reference level of ammonia in the exhaled air and with the exhalation of the patient. The presence of bacterial invasion is indicated by a change in the color of the indicator composition in the tube with the analyzed expiration. According to millimeter divisions, the increase in ammonia level relative to the standard is determined. The result is written in the analysis form manually. The duration of the examination is a quarter of an hour.
A more modern and accurate apparatus for carrying out a breath test is equipped with a digital sensor. The result is evaluated by the computer program, and it appears on the monitor in the form of a graph-histogram, which can be printed. In these devices a special mouthpiece is supposed, which protects the breathing tube from getting into it saliva. Time of the test is nine minutes. Provides the greatest accuracy.
The advantage of this equipment over other diagnostic methods, in addition to the already noted safety and the absence of contraindications, are portability and compactness, which allows to carry out an examination literally at the patient's bed under the supervision of the average medical staff. To determine the results, it is not necessary to transport the biomaterial in the laboratory. The analysis data do not depend on the age, physical condition and nature of the gastrointestinal tract.
Patients who underwent examination and received any positive results of a breath test for Helicobacter should, without delay, consult a doctor and undergo a course of treatment, which will avoid a multitude of unpleasant consequences.