What is the confirmatory test for Helicobacter pylori (H. pylori) diagnosis?

Confirmatory Tests for Helicobacter pylori Diagnosis

The urea breath test (UBT) and stool antigen test are the recommended confirmatory tests for diagnosing active Helicobacter pylori infection, with both tests demonstrating excellent sensitivity (94-97% for UBT and approximately 93% for stool antigen test) and specificity (95% for UBT and 93% for stool antigen test). 1, 2, 3

Non-Invasive Diagnostic Tests

Urea Breath Test (UBT)

• Considered the most accurate non-invasive test with excellent sensitivity (94.7-97%) and specificity (95-95.7%) 2, 3
• Detects active H. pylori infection by measuring the urease activity of the bacterium in the stomach 2
• Part of the recommended "test and treat" strategy for young (<50 years) dyspeptic patients without alarm symptoms 2, 3
• Patients should fast for at least 6 hours before the test for optimal accuracy 2

Stool Antigen Test

• Directly detects H. pylori bacterial antigens in stool specimens with sensitivity and specificity of approximately 93% 1, 3
• Comparable to UBT in accuracy and an excellent alternative for both initial diagnosis and post-treatment confirmation 1
• More practical than invasive methods, avoiding discomfort, expense, and potential complications of endoscopy 1
• Laboratory-based validated monoclonal stool antigen test is specifically recommended 3

Invasive Diagnostic Tests (Requiring Endoscopy)

Histological Examination

• Considered the gold standard among invasive tests 4
• Requires at least two biopsy samples from the antrum and body for improved sensitivity 5
• Several staining methods are available, with modified Giemsa being preferred due to its sensitivity, low cost, ease of use, and reproducibility 5
• Immunohistochemistry is the established gold standard for histology with high sensitivity and specificity 5

Rapid Urease Test (RUT)

• Based on the activity of H. pylori urease enzyme which splits urea to form ammonia 5
• Pre-treatment sensitivity ranges from 80-95% with specificity of 95-100% 5
• Requires approximately 10^4 organisms for a positive result 5
• Quick results available during endoscopy, making it cost-effective for initial evaluation 4

Culture

• Definitive proof of infection and allows for antimicrobial susceptibility testing 5
• Technically demanding with variable sensitivity between laboratories 5
• Particularly valuable after treatment failure when antimicrobial resistance is suspected 3

Important Considerations

• False negative results can occur with all tests except serology if patients have recently taken:

  • Proton pump inhibitors (should be discontinued at least 2 weeks before testing) 1, 3
  • Antibiotics (should be discontinued at least 4 weeks before testing) 3
  • Bismuth compounds 1, 3

• Serological tests are not recommended for confirming active infection because:

  • They cannot distinguish between active infection and past exposure 5, 3
  • Antibody levels persist in blood long after eradication 3
  • Overall accuracy of commercial ELISA serology tests averages only 78% 3

• For confirmation of eradication, testing should be performed no earlier than 4 weeks after completion of treatment 3

Algorithm for H. pylori Testing

1. For initial diagnosis in primary care setting:

   • First choice: 13C-urea breath test or laboratory-based monoclonal stool antigen test 3
   • If patient has recently used antibiotics or PPIs: wait 2 weeks after stopping these medications 3

2. For patients requiring endoscopy (those with alarm symptoms or age ≥50 years with new-onset dyspepsia):

   • Perform rapid urease test, histology, or culture during endoscopy 3
   • Consider immunohistochemical staining when results are equivocal 3

3. For confirmation of eradication:

   • Use UBT or stool antigen test at least 4 weeks after completion of treatment 3
   • Never use serology to confirm eradication 3