Testing for H. pylori in Patients with Previous Infection
For patients with a previous H. pylori infection, either the urea breath test (UBT) or stool antigen test (SAT) should be used to check for current infection, as these tests detect active infection rather than past exposure. 1
Recommended Tests for Active H. pylori Infection
Urea Breath Test (UBT)
- Sensitivity and specificity both >90% 1
- Patient drinks a preparation containing labeled urea (13C or 14C)
- H. pylori bacteria metabolize the urea, producing labeled carbon dioxide that is measured in exhaled breath
- Gold standard for non-invasive detection of active infection 1
Stool Antigen Test (SAT)
- Comparable accuracy to UBT when using laboratory-based monoclonal antibody tests 1
- Sensitivity and specificity both >90% 1
- Requires collection of stool sample
- Laboratory-based tests are preferred over rapid in-office tests 1
Tests to Avoid
Serology Tests
- Should not be used to confirm eradication after H. pylori treatment 1
- Antibody levels often remain elevated for months after successful eradication (serologic "scar") 1
- Only useful for initial diagnosis, not for confirming cure 1
Important Considerations for Testing
Pre-Test Preparation
To avoid false negative results, patients should:
- Stop antibiotics and bismuth for at least 4 weeks before testing 1
- Stop proton pump inhibitors (PPIs) for at least 7 days before testing 1
- Fast for at least 6 hours before UBT 1
Timing of Post-Treatment Testing
- Testing to confirm eradication should be performed no earlier than 4 weeks after completion of treatment 1, 2
Clinical Scenarios Requiring Confirmation of Eradication
Confirmation of H. pylori eradication is strongly recommended in:
- Complicated peptic ulcer disease
- Gastric ulcer
- Low-grade gastric MALT lymphoma
- Cases where treatment has low efficacy
- Patients with poor compliance 1
Algorithm for Testing After Previous H. pylori Infection
First choice: Urea Breath Test (UBT)
- Highest sensitivity and specificity
- Easiest to perform and interpret
Alternative: Stool Antigen Test (SAT)
- Use validated laboratory-based monoclonal antibody test
- Avoid rapid in-office tests due to limited accuracy
If recent use of antibiotics, bismuth, or PPIs:
- Delay testing until appropriate washout period
- Or consider endoscopy with biopsy if immediate testing is necessary
Common Pitfalls to Avoid
- Using serology to confirm eradication (will remain positive for months after successful treatment) 1, 2
- Testing too soon after completion of treatment (wait at least 4 weeks) 1
- Failing to stop PPIs, antibiotics, or bismuth before testing 1
- Using non-validated or rapid in-office stool tests 1
By following these evidence-based recommendations, clinicians can accurately determine whether a patient with previous H. pylori infection has active infection requiring treatment, avoiding unnecessary antibiotic exposure and ensuring appropriate management.