No, the Hydrogen Breath Test and Urea Breath Test Are Completely Different Diagnostic Tests
The hydrogen breath test (HBT) and urea breath test (UBT) are entirely distinct diagnostic procedures that measure different substances for different clinical purposes—they are not the same test and should not be confused. 1, 2, 3
Key Differences Between the Two Tests
Urea Breath Test (UBT)
- Purpose: Specifically detects Helicobacter pylori infection in the stomach 1, 2
- Mechanism: Exploits H. pylori's urease enzyme, which splits labeled urea (¹³C or ¹⁴C) into ammonia and labeled CO₂ that appears in breath 1, 2
- What it measures: Labeled carbon dioxide (¹³CO₂ or ¹⁴CO₂) in exhaled breath 1, 4
- Substrate used: 75-100 mg of ¹³C-labeled urea or 37-185 kBq of ¹⁴C-labeled urea 1, 2
- Test duration: 10-30 minutes after urea ingestion 2
- Accuracy: Sensitivity 94.7-97%, specificity 95-95.7% 2
Hydrogen Breath Test (HBT)
- Purpose: Diagnoses small intestinal bacterial overgrowth (SIBO), carbohydrate malabsorption (lactose, fructose), and measures intestinal transit time 3, 5
- Mechanism: Measures hydrogen gas produced by bacterial fermentation of unabsorbed carbohydrates in the intestine 3, 5
- What it measures: Hydrogen gas (H₂) concentration in exhaled breath 3, 5
- Substrate used: Various carbohydrates including glucose, lactulose, lactose, or fructose 3, 5
- Test duration: 2-3 hours 5
- Clinical use: Identifies bacterial overgrowth by characteristic early rise in breath hydrogen at approximately 90 minutes 5
Critical Clinical Distinctions
The fundamental difference is what each test detects: The UBT measures labeled CO₂ from urease activity specific to H. pylori, while the HBT measures hydrogen gas from bacterial fermentation of carbohydrates. 1, 3, 4
Pre-Test Requirements Differ
- UBT requirements: Stop PPIs for 2 weeks, antibiotics/bismuth for 4 weeks, fast for 6 hours 2, 6
- HBT requirements: Varies by substrate used; primarily requires fasting and avoidance of certain foods that affect hydrogen production 3, 5
Equipment and Analysis Differ Completely
- UBT equipment: Mass spectrometer (for ¹³C), infrared spectrometry, or scintillation counter (for ¹⁴C) 2, 4
- HBT equipment: Hydrogen gas analyzer measuring H₂ concentration 3, 5
Common Pitfall to Avoid
Do not order a hydrogen breath test when you need to diagnose H. pylori infection—this is the wrong test entirely. The UBT is the gold standard non-invasive test for confirming H. pylori infection and post-treatment eradication. 2, 7 Conversely, do not order a UBT when evaluating for SIBO or carbohydrate malabsorption, as it will not provide the needed diagnostic information. 3, 5