Labeled Urea Drink Ingestion
Patient swallows urea labeled with a carbon isotope tracer.
- ¹³C / ¹⁴C: Isotope used (non-radioactive or trace radioactive)
- ~75 mg: Dose (typical urea tracer dose)
- Yes: Fasting required (improves test accuracy)
- ~minutes: Onset (reaches stomach quickly)
Why labeled urea
Short placeholder: tracer carbon lets us follow urea breakdown in breath.
Bacterial Urease Enzyme Splitting
H. pylori urease hydrolyzes urea into ammonia and carbon dioxide.
- Urease: Enzyme (H. pylori surface/cytoplasmic enzyme)
- NH₃ + CO₂: Products (from one urea molecule)
- Acid buffer: Purpose (ammonia neutralizes stomach acid)
- High: Specificity (few other gastric organisms produce it)
Why urease matters
Short placeholder: urease activity is the biomarker this test detects.
Labeled CO2 Production
Labeled CO2 diffuses into blood and travels to the lungs.
- Bloodstream: Transport (CO2 diffuses across gastric wall)
- Lungs: Destination (exchanged at alveoli)
- 10–30 min: Timing (peak labeled CO2 in breath)
- Mass spec / IR: Detection (measures isotope ratio)
From stomach to breath
Short placeholder: labeled carbon rides blood flow into exhaled air.
Breath Sample Collection
Patient exhales into a bag before and after the urea dose.
- Pre-dose: Baseline sample (measures natural isotope background)
- Post-dose: Test sample (taken at set time points)
- Delta value: Analysis (difference over baseline)
- Yes: Non-invasive (no blood draw needed)
Sampling protocol
Short placeholder: two breath samples bracket the urea challenge.
Positive / Negative Result Interpretation
Elevated labeled CO2 above threshold indicates active infection.
- ~4 delta: Cutoff (per-mil excess over baseline)
- ~95%: Sensitivity (high detection accuracy)
- ~95%: Specificity (low false positive rate)
- Diagnosis & cure check: Use (pre/post-treatment testing)
Reading the result
Short placeholder: high CO2 ratio means urease activity, meaning infection.
Short placeholder: test confirms active H. pylori infection non-invasively.