What are the recommended laboratory tests to diagnose Helicobacter pylori (H. pylori) infection?

Laboratory Tests for Diagnosing Helicobacter pylori Infection

H. pylori infection can be diagnosed using both invasive techniques requiring endoscopy and non-invasive techniques, with the urea breath test and stool antigen test being the preferred non-invasive methods for initial diagnosis in most clinical settings. 1

Diagnostic Options

Non-invasive Tests

1. Urea Breath Test (UBT)

   • Gold standard among non-invasive tests
   • Sensitivity: >95%, Specificity: >95%
   • Based on H. pylori's urease activity
   • Excellent for both initial diagnosis and post-treatment confirmation
   • Limitations: May be affected by recent PPI use, antibiotics, or bleeding 1

2. Stool Antigen Test

   • Comparable to UBT for initial diagnosis
   • Sensitivity: 93.2%, Specificity: 93.2% (pre-treatment)
   • Post-treatment sensitivity: 88.8-92.1%, specificity: 87.3-87.6%
   • Polyclonal antibody tests are widely available; monoclonal tests may offer improved accuracy
   • European Helicobacter Pylori Study Group recommends as alternative to UBT 1

3. Serology (Blood Tests)

   • Detects IgG antibodies against H. pylori
   • Useful for screening and epidemiological studies
   • Cannot distinguish between active and past infection
   • Less suitable for confirming eradication 1

4. Urine Antibody Tests

   • Rapid, non-invasive option
   • Results available in 10-20 minutes
   • Sensitivity: 93.7-100%, Specificity: 88.9% 2

Invasive Tests (Requiring Endoscopy)

1. Histological Examination

   • Sensitivity: 90-95%, Specificity: 95-98%
   • Requires at least two biopsy samples (antrum and body)
   • Special stains improve detection (immunohistochemistry, modified Giemsa, Warthin-Starry) 1

2. Rapid Urease Test

   • Quick results (minutes to hours)
   • Based on urease activity of H. pylori
   • Less sensitive when bacterial density is low 1

3. Culture

   • Allows antibiotic susceptibility testing
   • Technically demanding with lower sensitivity
   • Essential for antimicrobial resistance testing 1

4. PCR-Based Methods

   • High sensitivity and specificity
   • Can detect low bacterial counts
   • Useful for identifying specific virulence factors and antibiotic resistance genes 3

Clinical Algorithm for H. pylori Testing

For Young (<50 years) Dyspeptic Patients Without Alarm Symptoms:

1. First-line: Non-invasive testing with UBT or stool antigen test
2. If positive: Treat for H. pylori
3. Post-treatment: Confirm eradication with UBT or stool antigen test (at least 4 weeks after completion of therapy) 1

For Patients With Alarm Symptoms or Age >50 Years:

1. First-line: Endoscopy with biopsy
2. Recommended biopsies: At least two samples (antrum and body)
3. Testing on biopsies: Histology and/or rapid urease test
4. Consider culture: For patients who have failed eradication therapy to determine antibiotic susceptibility 1

Common Pitfalls and Caveats

• False negatives can occur with all tests if the patient has recently taken:

  • Proton pump inhibitors (within 2 weeks)
  • Antibiotics (within 4 weeks)
  • Bismuth compounds (within 2 weeks)

• Combination of tests may be necessary for definitive diagnosis, as no single test is 100% reliable 1

• Post-treatment testing should be performed at least 4 weeks after completion of therapy to avoid false negative results 1

• Serology remains positive for months to years after successful eradication and should not be used to confirm cure 1

The "test and treat" strategy using non-invasive methods has been shown to be cost-effective and safe for young patients with dyspepsia, reducing the need for endoscopy while maintaining good clinical outcomes 1.