H pylori Tests and results

H Pylori Tests and Results

Helicobacter pylori may be diagnosed by several invasive or noninvasive Tests:

  • Histologic examination of gastric mucosa: Organisms stain poorly with H&E but may be demonstrated with Giemsa or silver staining.
  • The culture of gastric mucosa: Special culture techniques are required for isolation. The organism is microaerophilic and capnophilic and yields growth within 5 days on enriched media.
  • Urease activity (direct tissue or Urease breath test): Strongly positive.
  • Specific antigen: A commercially available assay for detection of H. pylori antigen in faeces shows a sensitivity of approximately 90% and specificity of approximately 95% for detection of active infection. Helicobacter pylori antigen may be useful for monitoring response to therapy.
  • Serology: Helicobacter pylori antibody IgG is typically measured. Positive response is predictive of active infection in patient populations where the prevalence of active infection is not high. Antibody levels may remain persistently positive for a period after successful therapy, so serology may have a limited role in an early test of cure.

Ammonia is derived mostly from protein degradation. Most of the ammonia in the blood comes from the intestine, where colonic bacteria use ureases to break down urea to ammonia and CO2. Eight-five percent of blood from the intestine is carried directly to the liver via the portal vein and 85% of ammonia is converted back to urea and excreted by the kidneys and colon. Helicobacter pylori in the stomach appear to be an important source of ammonia in patients with cirrhosis.

Normal range: <50 μmol/L.

The Urease breath test

The urea breath test (UBT) allows a non-invasive diagnosis of infection by Helicobacter pylori.  The bacterial toxins weaken the stomach protective mucus allowing the stomach cells to be susceptible to the damaging effects of acid and pepsin. It has been discovered that the bacterium produces urease, an enzyme that makes it possible to dissociate the urea molecule (N2H4CO) into ammonia (NR|OH) and carbon dioxide (CCh), so the presence of the bacterium can be revealed by detecting the enzymatic activity of urease. The urease enzymatic activity can be assessed by measuring the chemical conversion of urea to carbon dioxide in a breath test.

urea breath test  procedure & Instructions

The  13 OR 14 C-urea breath test ( 13 C-UBT) requires the patient to swallow an isotopically labelled ( 13 C OR 14C) urea tablet. The urea is subsequently hydrolyzed to ammonia and labelled CO 2  by the presence of H. pylori  urease activity. After approximately 30 minutes, an exhaled breath sample is collected, and  13 CO 2  levels are assessed using isotope ratio mass spectrometry.  An increase of more than 5% in the I3C breath content is considered as the definite sign of the Helicobacter Pylori infection .

urea breath test normal range

A value of <3/5 is taken as normal, the value of the isotopic ratio may be determined to detect a defined absorbing line for each one of the two isotopes and to calculate the ratio between the respective intensities. The natural isotopic content of the I3C isotope in the breath is 1.095% of the total CCh, and very low amounts of I3C are involved in increasing the isotopic ratio of 5%. The precision reached by TOLAS is sufficient to perform the analysis.

urea breath tests results

Negative:  <5 0 disintegrations per minute (DPM) for  H. pylori  

5 0–199 DPM indeterminate for  H. pylori    

>2 00 DPM positive for  H. pylori  

A sensitive analysis of trace gases in the exhaled breath is possible through the high-resolution molecular Spectroscopy based on tunable diode laser (TOLAS). An exemplary application of TDLAS in gastroenterology is the diagnosis of the Helicobacter pylori infection through the urea breath test based on the measurement of the i3CO2/12CO2 isotopic ratio in the exhaled breath.

 urea breath tests cost

Estimated costs of the urea breath test is between 50 – 80 $

H Pylori Stool Test

H Pylori Stool Test also knows the faecal culture, is an examination the war store excrement expelled from the digestive tract. Stool culture sardine evaluates diarrhoea of unknown aetiology, to identify the presence of parasites in the lower gastrointestinal tract, and to identify organisms that cause damage to intestinal tissue. Excessive flatus and abdominal discomfort are additional indications for stool culture. It must be noted that faeces of a healthy individual contains a significant number and variety of organisms that are not always pathogenic.

Testing is requested for evaluation of patients with dyspepsia or other upper GI symptoms suggesting H. pylori infection. Stool specimens, collected and transported using standard laboratory methods. Testing may be submitted to monitor the effect of treatment for H. pylori infection. Stool antigen becomes undetectable with effective therapy.

The presence of  H. pylori– specific IgG antibodies has been shown to be an accurate indicator of H. pylori  colonisation. H Pylori Stool Test  relies on the presence of  H. pylori  IgG-specific antibody to bind to antigen on the solid phase, forming an antigen-antibody complex that undergoes further reactions to produce a colour indicative of the presence of antibody and is quantified using a spectrophotometer or ELISA microwell plate reader. The sensitivity is 94% and specificity 78%, compared with an invasive procedure, such as biopsy, for which the sensitivity is 93% and specificity 99%.

H Pylori Stool Test Interpretation:

Expected result: Negative.

Positive result:

Active H. pylori infection. False-positive results may be seen in approximately 5% of tests.

Negative result:

The patient is unlikely to have active infection with H. pylori.

False-negative results may be seen in 5–7% of patients; repeat testing or testing with other types of assays for infection should be considered in patients with high suspicion for H. pylori infection.

The H Pylori Stool Test is used to monitor response during therapy and to test for a cure after  treatment.

H Pylori Stool Test Cost

faecal antigen immunoassay and [13C] urea breath test have excellent sensitivity and specificity (> 95%) at a cost of < $60

H Pylori Antibody Test

Laboratory-based serologic testing to detect H. pylori, H pylori antibody test is inexpensive and noninvasive. This is the predominant serologic test available for clinical use, and it is well suited to primary care practice. However, concerns over its accuracy have limited its use. Large studies have found that it has high sensitivity (90–100%) but variable specificity (76–96%); the accuracy has ranged from 83 to 98%.

IgA testing Vs IgG testing

Some studies found that IgA antibodies may detect cases that were negative by IgG testing. However, a number of studies have demonstrated that IgA testing is overall less sensitive and less specific than IgG testing. Some laboratories also offer IgM tests, which if elevated would indicate an acute infection. IgM assays have little or no role in clinical practice for the diagnosis or management of what is almost always a long-standing condition by the time H. pylori infection is considered.

H Pylori antibody test Interpretation:

Positive result:

Indicates that H. pylori IgG antibodies were detected in the sample. The presence of IgG antibodies to H. pylori is an indication of previous exposure to the organism.

Negative result:

Indicates that H. pylori IgG antibodies were not detected in the sample. Negative results by this test do not preclude recent primary infection.

Normal range FOR H Pylori antibody test is Negative.

H pylori antibody test Limitations:

  • The ACG guidelines recommend that testing for H. pylori should be performed only if the clinician plans to offer treatment for positive results.
  • Testing is indicated in patients with active peptic ulcer disease, a past history of documented peptic ulcer, or gastric MALT lymphoma.
  • The test-and-treat strategy for H. pylori (i.e., test and treat if positive) is a proven management strategy for patients with uninvestigated dyspepsia who are younger than 55 years of age and have no “alarm features” (bleeding, anemia, early satiety, unexplained weight loss, progressive dysphagia, odynophagia, recurrent vomiting, family history of GI cancer, previous esophagogastric malignancy).
  • Deciding which test to use in which situation relies heavily on whether a patient requires evaluation with upper endoscopy and an understanding of the strengths, weaknesses, and costs of the individual test.
  • General population screening of asymptomatic patients not recommended.
  • Patients with family history of GI cancer should have to screen if symptomatic (endoscopy with biopsy).
  • Patients without “alarm” symptoms, a dyspepsia that does not respond to antireflux treatment, may be candidates for H. pylori testing.

 

H Pylori antibody test Cost and Accuracy:

Laboratory-based quantitative serologic ELISA tests have an overall accuracy of only 80%. In comparison

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