Urea Breath Test for H.Pylori (Helicobacter Pylori)

Sample

• Two breath samples.

Purpose of the test (Indications)

1. This test is used to detect Helicobacter Pylori infection.
2. Advised in patients with recurrent:
   1. Chronic gastritis.
   2. Duodenal ulceration.
   3. Duodenal inflammatory process.

Pathophysiology

1. Helicobacter pylori (H.pylori) is a gram-negative bacillus. This was known as Campylobacter pylori.
2. Urea formation is summarized as follows.

3.   Urea formation takes place by the proteolysis of protein and the main site is the liver.
   

   Urea formation and the role of liver

4. H.pylori inhabit the mucous of the gastric mucosa.
   1. These bacteria are found in the mucus of the gastric mucosa.
   2. These bacteria cause damage to mucosa where HCL leads to ulcer formation.

5. This is also considered as carcinogenic (class 1 gastric carcinogen).
6. The colonies of H.Pylori are seen in:
   1. Duodenal ulcer = 90 to 95% .
   2. Gastric ulcer = 60 to 70%.
   3. gastric cancers = 20 to 25%.
      1. Around 10% of the young healthy people <30 years of age have the colonies of H.pylori.
      2. Gastric colonization by the H.pylori increases with age.
      3. Most of these patients remain asymptomatic and never develop an ulcer.
7. This is a risk factor for the:
   1. Gastric ulcer.
   2. Chronic gastritis.
   3. Duodenal Ulcer.
   4. Ulcerative esophagitis.

The principle of Urea Breath test:

1. H.pylori converts urea into  CO2 due to the presence of the urease enzyme.

2. Give orally radiolabelled urea (containing nonradioactive isotope ¹³C).
3. In gastric mucosa, if H.Pylori present then it will convert urea into  CO2 (¹³C).
4. This CO2 (¹³C) labeled passes through blood and goes to the lung.
5. Now measure CO2 (¹³C)  by:
   1. Gas chromatography.
   2. Mass spectrometer.
6. Procedure Two breath samples.
   1. First, take a sample before giving the isotope-labeled (¹³C) urea.
   2. Second after 30 minutes of a dose of isotope-labeled (13C) urea.
7. Specificity and sensitivity are 95% and the test is cheap to diagnose in comparison to invasive procedures.

Normal

• Breath test (Source 4)
  • <50 DPM for H. pylori.
  • 50 to 199 DPM for H. pylori
  • >200 DPM positive for H. pylori.
• < 3 % .
• A positive test means H. Pylori infection.
• Source 1
• Serology:
  • The presence of IgG and IgA antibodies are seen in 81 to 100% of the patient with gastritis.
  • But in only 25% of the patients without histological evidence of H. pylori.
  • The testing of IgM is not helpful.

False-negative test:

1. You can get a false negative test if the patient uses antacids within a week prior to the test.
2. The patient should not use any antibiotics and bismuth for one month.
3. No proton pump inhibitors and sucralfate for two weeks before the test.
4. The patient should be at rest during the collection of breath.

Diagnosis of H. pylori:

It can be diagnosed by the following tests>

1. Positive breath test.
2. Presence of specific antibody. Sensitivity is 94% and specificity is 78%.
3. Positive culture.
4. A positive biopsy is done by endoscopy. Sensitivity is 93% and specificity is 99%.
5. The stool is examined for the H. pylori antigen.

---