What is the purpose and procedure of the urea breath test (UBT) for diagnosing Helicobacter pylori (H. pylori) infection?

Urea Breath Test for Diagnosing Helicobacter pylori Infection

The urea breath test (UBT) is a highly accurate, non-invasive diagnostic test that detects active Helicobacter pylori infection by measuring the urease activity of the bacterium in the stomach. 1

Purpose of the UBT

• The UBT is primarily used to diagnose active H. pylori infection, which is associated with peptic ulcer disease, chronic gastritis, and gastric malignancies 1
• It serves as an excellent tool for confirming successful eradication after H. pylori treatment 2
• The test is particularly valuable for epidemiological studies and for screening patients before endoscopy 3
• UBT is part of the "test and treat" strategy recommended for young (<50 years) dyspeptic patients without alarm symptoms, reducing the need for invasive endoscopy 1

Procedure of the UBT

Test Principle

• The test exploits H. pylori's abundant production of the enzyme urease 3
• When isotopically labeled urea is ingested, H. pylori's urease hydrolyzes it into ammonia and labeled carbon dioxide 1
• The labeled CO₂ diffuses into the bloodstream and is exhaled in the breath, where it can be measured 1

Test Protocol

• The patient ingests urea labeled with either ¹³C (non-radioactive) or ¹⁴C (radioactive) isotopes 2
• A test meal is typically given to increase contact time between the tracer and H. pylori urease in the stomach 3
• Breath samples are collected at baseline (before urea ingestion) and after ingestion (typically at 30 minutes) 1
• The samples are analyzed to measure the labeled CO₂, with results expressed as delta over baseline (DOB) for ¹³C or disintegrations per minute (DPM) for ¹⁴C 4

Test Variants

• ¹³C-UBT uses a stable, non-radioactive isotope and is preferred for children and pregnant women 2
• ¹⁴C-UBT uses a radioactive isotope with minimal radiation exposure, but ¹³C is generally preferred despite higher cost 2, 5
• Newer tablet formulations of ¹³C-urea allow for faster testing (as little as 10 minutes) and avoid interference from urease-producing bacteria in the oropharynx 1

Test Performance

• The UBT has excellent diagnostic accuracy with sensitivity of 94.7-97% and specificity of 95-95.7% 1
• It is considered superior to serological tests, which only indicate past exposure rather than active infection 1
• The UBT is comparable in accuracy to the stool antigen test, which is another non-invasive option for detecting active infection 1

Important Considerations and Pitfalls

• False negative results can occur if the patient has recently taken:

  • Antibiotics (should be withheld for at least 4 weeks before testing) 1
  • Bismuth products (should be withheld for at least 2 weeks) 1
  • Proton pump inhibitors (should be withheld for at least 7 days) 1

• False positive results may occur in:

  • Patients with achlorhydria or atrophic gastritis due to urease-producing non-H. pylori organisms 1
  • When suspected, confirmation with a stool antigen test or endoscopy is recommended 1

• Low UBT values in H. pylori-positive patients may be associated with increased risk of gastric cancer due to more severe atrophic gastritis 6

• For optimal accuracy, patients should fast for at least 6 hours before the test 1

• Some centers establish an indeterminate range of values that warrant repeat testing to avoid unnecessary antibiotic treatment 4

Clinical Applications

• The UBT is ideal for confirming eradication 4-6 weeks after completion of H. pylori treatment 2
• It's valuable for diagnosing H. pylori when endoscopic biopsies cannot be taken (e.g., in patients on anticoagulants) 2
• The test is particularly useful in the "test and treat" strategy for young dyspeptic patients without alarm symptoms 1
• UBT results can help guide clinical decisions regarding the need for further investigation or treatment 1