Urea Breath Test for H. pylori Diagnosis
Primary Recommendation
The urea breath test (UBT) is the preferred non-invasive diagnostic test for detecting active Helicobacter pylori infection, with excellent accuracy (sensitivity 94.7-97%, specificity 95-95.7%) and should be your first-line choice for both initial diagnosis and post-treatment confirmation of eradication. 1, 2, 3
How the Test Works
The UBT exploits H. pylori's abundant production of urease enzyme. When patients ingest isotopically labeled urea (¹³C or ¹⁴C), the bacterial urease hydrolyzes it into ammonia and labeled CO₂, which diffuses into the bloodstream and is exhaled within minutes, where it can be measured. 4, 5, 6
Choose ¹³C-urea over ¹⁴C-urea because it is non-radioactive and safe for children and pregnant women, whereas ¹⁴C involves radiation exposure. 4, 1, 7
Critical Pre-Test Preparation (Most Common Cause of Test Failure)
Medication Washout Requirements
Stop proton pump inhibitors (PPIs) for at least 2 weeks before testing - this is the most common pitfall, as PPIs cause 10-40% false-negative rates by reducing bacterial load. 1, 2, 3
Discontinue antibiotics and bismuth compounds for at least 4 weeks - these temporarily suppress H. pylori and produce false-negatives. 1, 2, 3
H2-receptor antagonists cause fewer false-negatives than PPIs and guidelines do not mandate stopping them when using citric acid test meals. 2
Patient Preparation
Test Administration Protocol
Administer 75 mg of ¹³C-labeled urea with a test meal to delay gastric emptying and allow even distribution throughout the stomach. 1
Use tablet formulations rather than liquid forms - tablets avoid interference from urease-producing bacteria in the oropharynx. 1
Collect the second breath sample 10-30 minutes after urea ingestion for optimal accuracy. 1, 8, 5
Interpreting Results
When to Trust a Positive Result
A positive UBT result is reliable even if the patient was recently on medications - PPIs and antibiotics cause false-negatives, not false-positives. 1
When to Question a Negative Result
False-negatives occur with inadequate medication washout - this is the most common error in clinical practice. 1
Patients with low bacterial load (premalignant or malignant gastric lesions) may have false-negative results; consider endoscopy with biopsies if clinical suspicion remains high despite negative UBT. 1
False-positives may occur in patients with achlorhydria or atrophic gastritis due to urease-producing non-H. pylori organisms. 1, 3
Clinical Applications
Primary Diagnosis
The UBT is ideal for the "test and treat" strategy in young patients (<50 years) with dyspepsia and no alarm symptoms, avoiding the need for invasive endoscopy. 3
Post-Treatment Confirmation
The UBT is the gold standard for confirming successful eradication - perform testing 4-6 weeks after completing treatment to avoid false-negatives. 4, 8, 9
Special Situations
When endoscopy finds an ulcer but biopsies cannot be taken (e.g., patients on anticoagulation), the UBT is the ideal diagnostic tool. 8
For epidemiological studies, the UBT provides information about active infection, unlike serology which only indicates past exposure. 3, 8
Comparison to Alternative Tests
The UBT outperforms the stool antigen test (UBT: 94.7% sensitivity/95.7% specificity vs. stool test: 88.8% sensitivity/87.3% specificity), making it the preferred choice when available. 2
The UBT is vastly superior to serology, which only detects antibodies from past exposure rather than active infection. 3
Equipment Requirements
For ¹³C-UBT: Mass spectrometer, infrared spectrometer, or laser-assisted ratio analyzer to measure exhaled ¹³CO₂. 1, 5
For ¹⁴C-UBT: Scintillation counter to measure radioactivity. 1
The higher equipment cost is offset by superior accuracy and the ability to test children and pregnant women safely. 2, 5