What is the recommended approach for H. pylori (Helicobacter pylori) serology testing?

Recommended H. pylori Serology Testing Approach

For initial diagnosis of H. pylori infection, urea breath test (UBT) and laboratory-based monoclonal stool antigen tests are preferred over serology due to their superior accuracy in detecting active infection. 1 Serology should be reserved for specific clinical scenarios where other tests might yield false negatives.

Non-Invasive Diagnostic Options for H. pylori

Tests for Active Infection (Preferred)

1. 13C-Urea Breath Test (UBT)

   • Gold standard non-invasive test
   • Sensitivity and specificity >90% 1
   • Easy to perform and highly accurate
   • Requires withholding:
     • Antibiotics and bismuth for 4 weeks
     • PPIs for 7 days
     • Food for 6 hours before testing 1

2. Stool Antigen Test (SAT)

   • Only use laboratory-based monoclonal antibody tests
   • Accuracy equivalent to UBT (>90% sensitivity/specificity) 1
   • Avoid rapid in-office stool tests (limited accuracy) 1
   • Same medication restrictions as UBT

Serological Testing (Limited Use)

• Validated IgG ELISA tests only
  • Commercial tests vary significantly in accuracy
  • Only use tests with validated accuracy >90% 1
  • Local validation recommended due to regional strain variations 1

When to Use Serology Testing

Serology is appropriate in specific clinical scenarios:

1. Recent use of antimicrobials or antisecretory drugs 1
2. Active GI bleeding 1
3. Atrophic gastritis or gastric malignancies 1
4. Low bacterial load conditions where UBT/SAT may be falsely negative 1

Important Limitations of Serology

• Only indicates past exposure, not active infection 1
• Cannot differentiate between current and previously eradicated infections 1
• Should not be used to confirm cure after treatment 1
• Positive predictive value drops significantly in low-prevalence populations 1
• Office-based rapid serologic tests have disappointing accuracy (63-97% sensitivity, 68-92% specificity) and are not recommended 1

Algorithm for H. pylori Testing

1. First-line testing (for initial diagnosis):

   • UBT or laboratory-based monoclonal SAT

2. Use serology instead when:

   • Patient has taken antibiotics in past 4 weeks
   • Patient has taken PPIs in past 7 days
   • Patient has active GI bleeding
   • Suspected gastric atrophy or malignancy

3. Post-treatment confirmation:

   • UBT or monoclonal SAT only (never serology)
   • Test at least 4 weeks after completing therapy
   • Serology remains positive for months to years after eradication 1

Special Considerations

• In primary care settings, laboratory serology is acceptable if properly validated locally 1
• For patients <45 years with dyspeptic symptoms and no alarm features, test-and-treat strategy using non-invasive tests is appropriate 1
• Patients >45 years with dyspeptic symptoms or any patient with alarm symptoms should be referred for endoscopy rather than non-invasive testing 1

By following these evidence-based recommendations, clinicians can optimize the accuracy of H. pylori diagnosis while minimizing unnecessary treatments and their associated risks.