How does the Helicobacter test work?

The question of whether Helicobacter pylori bacteria can be detected in the ulcer patient is very important, as the presence or absence of the pathogen has a major impact on the treatment. Methods of detection are discussed in detail below.

Helicobacter test

Invasive methods

By invasive methods we mean Helicobacter pylori determinations from tissue samples taken during gastroscopy.

  1. Rapid urease test: the tests involve placing the tissue sample in a liquid or gel containing urea, in which the bacterial urease enzyme causes the urea to decompose. This is indicated by a yellow to red colour reaction. The test result can be read within 2-24 hours. The disadvantage of the test is that the factory-made tests are expensive and can give false negative results in the presence of a small number of pathogens and false positives in the presence of other bacteria that also produce urease enzyme. The sensitivity and hit rate of the test is above 90 %. Widely used method.
  2. Histopathology: sections of gastric mucosa samples can be used to detect Helicobacter pylori with high confidence using various special stains. This is currently the most widely used method for detecting the bacterium in Hungary. The disadvantage is that special staining procedures are also expensive.
  3. Culturing, antibiotic resistance testing: perhaps the most reliable way to detect Helycobacter pylori is to culture tissue samples. Another major advantage is that antibiotic susceptibility testing of the bacterium can detect strains resistant to certain antibiotics, allowing the bacterium to be eradicated with a targeted combination of other antibiotic treatments.
    The disadvantages of cultivation are the difficulty of transport (special transport medium) and the equipment requirements, as the bacterium can only be cultivated in an environment with 5 % of carbon dioxide.
  4. PCR technique: by polymerase chain reaction, Helicobacter pylori can be detected at almost 100 % from tissue samples or gastric juice, or, as a non-invasive method, from faeces and saliva. The method is only used in scientific studies due to its complexity and cost.

Non-invasive methods

  1. Serological tests: a method for detecting antibodies against Helicobacter pylori, which are determined from the patient's blood serum. There are rapid tests that give results in a few minutes from a drop of blood taken from a fingertip. The test can be performed in a laboratory setting from a traditionally drawn blood sample.
    The test is suitable for screening. The result of the test can be obtained quickly after the blood test.
    Unfortunately, the test is not a good way to measure the effectiveness of the medication used to eradicate the bacteria. This is because it is an indirect test. After Helicobacter pylori has been eradicated, the amount of antibodies in the bloodstream only slowly decreases, and it takes about six months before a false positive result is obtained.
    Test methods are now available to determine antibodies from saliva. In Hungary these are mainly used as screening tests in childhood and to assess the prevalence of the disease in the population.
  2. C13-urea breath test: A non-invasive testing method developed a few years ago. It has been developed in a recently developed technique. The bicarbonate is converted into carbon dioxide, labelled with the carbon atom isotope, which is carried by the circulation to the lungs and exhaled. From the resulting air sample, the non-emitting (non-radioactive) C13 isotope can be detected by mass spectrophotometer and the emitting (radioactive) C14 isotope by scintillation counter.
    The C13 (non-radiation) isotope-labelled test is the most common, and can be used in children and pregnant mothers. The radioactive-isotope method is less common, although its radiation exposure is a thousandth of that of an X-ray. The great advantage of this test is that it does not cause any discomfort to the patient and, unlike a serological test, the results after the test (24-48 hours) provide information on the current status. A C14-urea breath test the Endomedix Budapest and Miskolc gastroenterology centre, please ask our colleagues about the current availability of the test in our other centres.

The C13-ura test procedure

No special preparation is needed, but you should not eat or drink for 6 hours before the test. Scientific studies have shown that drugs that inhibit acid secretion (such as H2-receptor blockers and proton pump inhibitors) may affect the results, so such drugs should be discontinued until 5-7 days before the test (coagulants and antacids may be used).

The test starts with the consumption of skim milk or 100 % orange juice (2 dl). Then, after 5 minutes, the so-called baseline sampling is done by blowing into 2-3 normal test tubes with a straw so that the tube wall is humid. Another method is to blow into a small sealed bag or hose of about half a litre capacity instead of a test tube. The tubes or hoses are then resealed.

After 5 minutes, the urea marked C13 is mixed with water mixed with citric acid or plain tap water and the patient is asked to drink it. This liquid, which is about two and a half decilitres in volume, has no particular taste, but when mixed with citric acid it is slightly acidic.

After consuming the liquid, lie down for 2-3 minutes, first on one side and then on the other, on your stomach and on your back, so that the liquid can come into contact with the entire surface of the stomach. After 30 minutes, the next air samples should be taken, the blowing being carried out in the same way as before.

The samples are sent by post, packed in a small cardboard box, to the laboratory with the measuring equipment, from where the results are usually available in 1-3 days, depending on capacity and distance. The great advantage of the test is that the patient does not have to be sent to the laboratory where the test is carried out, it can be done at the local specialist clinic, GP surgery or even at the patient's home. The test can be used for screening, to measure the success of treatment and for longer-term follow-up.

Quote from our medical director, Dr. Alajos Takáts: Patient Education Book on Ulcer Disease (Springer Publishing, 1998). With updates by the author.