Urea Breath Test — H. pylori Infection
Test Characteristics
| Metric | Value |
|---|---|
| False-negative rate | 4% (sensitivity 96%) |
| False-positive rate | 7% (specificity 93%) |
| Bayes factor | 10× |
| Base rate | 30% of US adults overall |
Interpreting Results
| Scenario | Prior | + Result | − Result |
|---|---|---|---|
| Average US adult | 30% | 10 × 30% ≥ 100%30%× 10100% | 1/10 × 30% = 3%30%÷ 103% |
| Young white adult | 20% | 10 × 20% ≥ 100%20%× 10100% | 1/10 × 20% = 2%20%÷ 102% |
| Hispanic or African American, or age >60 | 55% | 10 × 55% ≥ 100%55%× 10100% | 1/10 × 55% = 5.5%55%÷ 105.5% |
All positive-test entries saturate. Exact posteriors (full Bayesian math): average US adult = 81%, young white adult = 71%, Hispanic/African American/age >60 = 92%. Negative-test exact posteriors at these high base rates: 4%, 2%, 11%. PPI use within 2 weeks and recent antibiotics can cause false negatives.
- + result: at a 30% base rate, risk pushes to 81%
- − result: risk drops to just under vegetarian (4%)
Sources:
- Systematic review, PMC, 2014. PMC 4306177.
- AAFP. Noninvasive diagnostic tests for H. pylori.
- StatPearls. Helicobacter pylori.