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False negative h pylori blood test: How To Do A Helicobacter Pylori Testing? |Gastro Health

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How To Do A Helicobacter Pylori Testing? |Gastro Health



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As previously discussed in our Fall 2012 issue, Helicobacter pylori (H. pylori) is a bacteria found in the stomach that can cause a variety of intestinal disorders such as peptic ulcers and gastritis. This bacterium is also a very common cause for dyspepsia, a syndrome consisting of epigastric discomfort, feelings of early fullness after eating, and bloating.

For patients who do not have “alarm” symptoms such as weight loss or vomiting which require a more thorough evaluation, non-invasive testing for H. pylori can easily and effectively diagnose the presence of this bacterium. One such test that is commonly available now is a urea breath test. This test can be used to both diagnose Helicobacter pylori and confirm its eradication. The test requires a patient to provide a sample of their breath about 20 minutes after ingesting a compound. This is based on the fact that H. pylori can covert a compound called urea to both carbon dioxide and ammonia.

During this test, a patient will ingest a detectable type of carbon called an isotope. If H. pylori is present, this isotope will incorporate into carbon dioxide and will then be detectable in the patient’s breath. There are two commercially available tests, and the only difference between these tests is the use of a radioactive isotope in one of the tests. It should be noted that the amount of radiation used in the test is essentially equal to the normal radiation a person is exposed in their daily life.

The urea breath test has a reported sensitivity and specificity of 95%, meaning the chance of a false positive test is very low. False negative tests can also occur, especially if a patient is being prescribed certain medications. The two classes of medications that can cause false negative results include antibiotics and proton pump inhibitors (PPIs) such as Nexium or Prilosec. These medications will suppress but not completely eliminate the presence of H. pylori in the stomach. In order to eliminate this risk, a patient must not use antibiotics for four weeks and PPIs for two weeks prior to undergoing the test.

Another option in terms of non-invasive evaluation is the use of an H. pylori stool antigen test. The antigen is essentially a marker for the presence of active bacteria. This test offers a similar accuracy as compared to urea breath testing in detecting the bacteria. However, it has a slightly higher chance of a false positive result in comparison to the urea breath test, and a similar chance of a false negative result. The main advantage of stool antigen testing is that it is slightly less costly as compared to the breath test.

The urea breath test is an increasingly common way for physicians to safely and accurately diagnose the presence of H. pylori in the most cost effective way possible. The increasing use of this test will undoubtedly lead to this bacterium to be more easily identified and thereby allow more and more patients to reap the benefits of treatment.


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Helicobacter Pylori

Somal S. Shah, MD


Gastroenterology
Internal Medicine


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Helicobacter Pylori (H. Pylori) is a bacteria found in the stomach. It was initially identified in 1982 when scientists discovered that this particular bacteria was present in patients suffering from chronic gastritis and gastric ulcers. Infection with H. Pylori can contribute to the development of gastritis (inflammation of the stomach), gastric or duodenal ulcers, and dyspepsia (upset stomach and or indigestion).


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Dyspepsia: When and How to Test for Helicobacter pylori Infection

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Helicobacter pylori, IgG (quantitative)

Detection of class G immunoglobulins (IgG) to Helicobacter pylori in blood serum, used to diagnose antral and fundal gastritis, gastric and duodenal ulcers, as well as to monitor their treatment.

Synonyms Russian

Helicobacter, class G immunoglobulins, IgG antibodies.

Synonyms English

Helicobacter pylori Antibody, IgG; Anti-Helicobacter pylori antibody, IgG (quantitative).

Research method *

Enzyme immunoassay.

* May vary by region.

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

Do not smoke for 30 minutes before the test.

General information about the study

H. pylori infection is accompanied by the development of a local and systemic immune response. Following a transient increase in the titer of class M immunoglobulins (IgM), a prolonged and significant increase in IgG-as well as IgA-antibodies in the blood serum follows. Determination of the concentration of immunoglobulins (serological examination) is used in the diagnosis of helicobacteriosis. IgG are found in 95-100% of cases of H. pylori infection, IgA – in 68-80%, and IgM – only in 15-20%. Therefore, to confirm infection with H. pylori, the concentration of IgG in the blood serum is determined. This analysis has a number of advantages over other laboratory methods for detecting Helicobacter pylori.

The determination of IgG in the blood does not require endoscopic examination, therefore it is a safer diagnostic method. Since the sensitivity of the test is comparable to that of most invasive tests (rapid urease test, histological examination), it is especially useful when endoscopy is not planned. However, it should be noted that the test does not directly detect the microorganism and depends on the characteristics of the patient’s immune response. So, for example, the immune response of the elderly is characterized by a reduced production of specific antibodies (any, including H. pylori), which must be taken into account if a negative test result is obtained with clinical signs of dyspepsia. In addition, the immune response is suppressed when taking certain cytotoxic drugs.

The IgG assay is most useful in diagnosing primary H. pylori infection (eg, in a young patient presenting with new onset of dyspepsia). In this situation, a high IgG titer suggests an active infection. Also, a positive test result in a patient (with or without a history of dyspepsia) who has not received therapy will indicate helicobacteriosis.

The interpretation of a positive test result if therapy has been performed (or if antibiotics with activity against H. pylori have been used for other purposes) has some peculiarities. The IgG level remains high for a long time after the complete death of the microorganism (about half of the patients cured of H. pylori will have high IgG titers for another 1-1.5 years). As a result, a positive test result in a patient treated with antibiotics does not allow differentiation between active infection and a history of infection and requires additional laboratory tests.

For the same reason, IgG testing is not the main test for diagnosing the effectiveness of therapy. However, it can be used for this purpose if the antibody titer at the onset of the disease is compared with the titer after the end of treatment. It is believed that a decrease in the concentration of IgG by 20-25% within 6 months indirectly indicates the death of the microorganism. At the same time, if this concentration does not decrease, this does not mean that the therapy is ineffective. The absence of IgG antibodies on re-analysis indicates the success of the treatment and getting rid of the microorganism.

The amount of IgG to H. pylori is also one of the components by which the state of the gastric mucosa is judged (this is the so-called serological biopsy).

What is research used for?

For diagnosing diseases caused by H. pylori and monitoring their treatment:

  • antral and fundic gastritis;
  • ulcers of the duodenum or stomach.

When is the examination scheduled?

  • When evaluating a patient with new onset of dyspepsia (primary H. pylori infection), especially if endoscopy is not planned.
  • When examining a patient with a history of dyspepsia, if H. pylori therapy was not prescribed (or if antibiotics active against H. pylori were not used for another reason).
  • During the primary diagnosis of helicobacteriosis and 6 months after the end of the course of its therapy.

What do the results mean?

Reference values: *

*Reference values ​​vary for some regions due to the use of different test systems for the study.

Reason for positive result

  • Active H. pylori infection:

a) a decrease in antibody titer by 20-25% within 6 months after the end of antibiotic therapy indirectly indicates the death of the microorganism;

b) the absence of a trend towards a decrease in IgG does not indicate the ineffectiveness of therapy.

  • history of H. pylori infection.

Reason for negative result:

  • no H. pylori infection;
  • death of a microorganism after a course of antibiotic therapy.

What can influence the result?

The immune response of the elderly, as well as patients receiving immunosuppressive therapy, is characterized by a reduced production of specific antibodies, including H. pylori, which leads to a greater number of false negative test reactions in this group of patients.

Important notes

  • A positive test result should be interpreted in the light of additional data (in particular, eradication therapy or use of antibiotics active against H. pylori for other purposes should be considered).

Also recommended

  • Helicobacter pylori DNA [real-time PCR]
  • Helicobacter pylori, IgA
  • Helicobacter pylori antigen
  • Gastrin
  • Pepsinogen I
  • Pepsinogen II
  • Antibodies to parietal cells of the stomach
  • Laboratory examination – gastritis and gastric ulcer
  • Laboratory diagnosis and monitoring of atrophic gastritis and peptic ulcer disease
  • Fecal occult blood test
  • Coprogram

Who orders the examination?

Gastroenterologist, pediatrician, general practitioner, infectious disease specialist.

Literature

  • Glupczynski Y. Microbiological and serological diagnostic tests for Helicobacter pylori: an overview. Br Med Bull. 1998;54(1):175-86.
  • Mark Feldman, MD; Byron Cryer, MD; Edward Lee, MD; Walter L. Peterson, MD. Role of Seroconversion in Confirming Cure of Helicobacter pylori Infection. JAMA. 1998;280(4):363-365. doi:10.1001/jama.280.4.363.
  • Athanasios Makristathis, Alexander M. Hirschl, Philippe Lehours, Francis Mégraud , . Diagnosis of Helicobacter pylori infection. Helicobacter. Volume 9, Issue Supplement s1, pages 7–14, August 2004.
  • Chernecky C. C. Laboratory Tests and Diagnostic Procedures / C.S. Chernecky, V.J. Berger; 5th ed. – Saunder Elsevier, 2008.

To know is to win. Diagnosis of Helicobacter pylori

Articles for patients
/ To know is to win. Diagnosis of Helicobacter pylori

9He licobacter р ylori transcription – X (G) elicoba kter pilo ́ ri – spiral gram-negative bacterium that infects various areas of the stomach dka and duodenum Many cases of gastric and duodenal ulcers, gastritis, duodenitis, cancer stomach and, possibly, some cases of gastric lymphomas are etiologically associated with infection Helicobacter pylori . However, the majority (up to 90%) of infected carriers of Helicobacter pylori do not show any symptoms of the disease.

The spiral shape of the bacterium, from which the generic name Helicobacter is derived, is believed to determine the ability of this microorganism to penetrate the mucous membrane of the stomach and duodenum and facilitate the movement of the bacterium in the mucous gel that covers the gastric mucosa.

The bacterium was rediscovered in 1979 by Australian pathologist Robin Warren, who then conducted further studies with Barry Marshall starting in 1981. Warren and Marshall were able to isolate and isolate this microorganism from samples of the human gastric mucosa. They were also the first to succeed in cultivating this microorganism on artificial nutrient media.

In 2005, the medical discoverers of the bacterium Robin Warren and Barry Marshall were awarded the Nobel Prize in Medicine.

There are several methods for determining H. pylori infection.

1. Non-invasive (not requiring endoscopy) tests for the presence of H. pylori infection:

– definition 9000 6 antibody titer in blood to antigens H . pylori . One step immunochromatographic method. May give false negative results due to low colonization of bacteria in the stomach, resulting in low concentrations of H. pylori antigens in faeces and failure to respond in the test. False-negative results may also be caused by uneven distribution of the antigen in the feces, destruction of the antigen by slowing down the evacuation of feces (constipation), gastrointestinal bleeding .

Detection of class G and A immunoglobulins to H. pylori in blood serum. May give false negative results in patients with a weak immune response, an early stage of infection. Diagnostic accuracy varies with duration of exposure to the bacterium, cross-antigenicity with other antigenically related bacteria, degree of gastritis, and contamination. In addition, antibodies persist for a long time after successful treatment, and it is difficult to use this method to check the success of the treatment. However, since H. pylori infection is chronic and its spontaneous clearance (complete and final self-healing only by the forces of the body) is impossible, positive antibody tests in untreated patients indicate the presence of an ongoing infection. Meanwhile, after successful treatment, the antibody titer decreases over time. The advantage of this method is that a blood test for antibodies can be done while taking antibiotics.

You can take these tests at any branch of the MBUZ CDC “Health”. Tests are taken from Monday to Friday, from 8.00-10.00, treatment room

– determination of the presence of antigens H 9 0006 . pylori kale . H. pylori detection, which uses real-time polymerase chain reaction (RT-PCR) to detect the genetic material (DNA) of a microorganism in a stool sample. The test is very sensitive to the quality of the test material, which can lead to false negative results, due to the fact that the test feces may contain substances that inhibit PCR: thermolabile proteins, glycolipids, DNA of other bacteria, complex polysaccharides (plant food residues), extracellular polysaccharides of other bacteria, blood, bile, excess inorganic salts, etc.

You can take this analysis at any branch of the MBUZ CDC “Health”. Analyzes are taken from Monday to Friday, from 8.