What is the recommended initial test to diagnose Helicobacter Pylori (H. Pylori)?

Diagnostic Approach to Helicobacter Pylori Infection

The urea breath test (UBT) is the recommended gold standard non-invasive test for initial diagnosis of H. pylori infection due to its excellent sensitivity (94.7%) and specificity (95.7%) for detecting active infection. 1

Non-Invasive Testing Options

First-Line Testing (No Endoscopy Required)

1. Urea Breath Test (UBT)

   • Gold standard non-invasive test
   • Sensitivity: 94.7%, Specificity: 95.7% 1
   • Detects active infection by measuring urease activity
   • Capsule-based UBT shows 100% sensitivity and specificity with single 10-minute breath sample 2
   • Requires stopping PPIs for 2 weeks before testing 1

2. Stool Antigen Test (SAT)

   • Excellent alternative to UBT with comparable accuracy
   • Sensitivity: 94-95%, Specificity: 97-100% 1
   • Only validated laboratory-based monoclonal tests should be used 3
   • Rapid in-office stool tests have limited accuracy and are not recommended 3, 1
   • Requires stopping PPIs, bismuth, and antibiotics for at least 2 weeks 1

3. Serology (IgG antibody tests)

   • Not recommended as first-line due to inability to distinguish active from past infection 1
   • Only validated IgG serology tests should be used (accuracy varies significantly) 3
   • Appropriate in specific scenarios:
     • When PPIs cannot be stopped for required 2 weeks
     • Recent antimicrobial use
     • Ulcer bleeding
     • Gastric atrophy or malignancies 3, 1

Invasive Testing Options (Endoscopy Required)

When endoscopy is indicated (patients >45-50 years with new-onset dyspepsia or those with alarm symptoms), the following tests can be performed:

1. Rapid Urease Test (RUT)

   • Based on H. pylori urease activity
   • Sensitivity: 80-95%, Specificity: 95-100% 3
   • Results available within hours
   • False negatives can occur with low bacterial density, PPI use, bleeding, or recent antibiotics 3

2. Histology

   • Sensitivity: 90-95%, Specificity: 95-98% 3
   • Improved by examining at least two samples from antrum and body 3
   • Modified Giemsa stain recommended (sensitive, cheap, reproducible) 3
   • Immunohistochemistry is gold standard for histological diagnosis 3

3. Culture

   • Definitive proof of infection
   • Allows antibiotic susceptibility testing
   • Technically demanding with variable sensitivity 3

Testing Algorithm

1. For patients <45-50 years without alarm symptoms:

   • Use "test and treat" strategy with non-invasive testing 1
   • First choice: Urea Breath Test (UBT)
   • Alternative: Laboratory-based monoclonal Stool Antigen Test (SAT)

2. For patients with any of the following:

   • Age >45-50 years with new-onset dyspepsia
   • Alarm symptoms (weight loss, anemia, dysphagia)
   • Failed eradication therapy
   • Recommendation: Endoscopy with biopsy for histology and rapid urease test 1

Important Considerations and Pitfalls

• Medication interference: Stop PPIs for 2 weeks, antibiotics and bismuth for 4 weeks before testing (except serology) 3, 1
• Post-treatment confirmation: Use UBT or SAT at least 4-8 weeks after completing therapy 1
• Never use serology to confirm eradication as antibodies remain elevated for months or years after successful treatment 3, 1
• Sampling error: Take at least two biopsy samples (antrum and body) when performing endoscopic testing 3
• False negatives: Can occur in bleeding patients, those on PPIs, or with low bacterial density 3

By following this diagnostic approach, clinicians can accurately diagnose H. pylori infection and appropriately guide treatment decisions to reduce the risk of peptic ulcer disease, gastric cancer, and other H. pylori-associated complications.