What is the recommended initial test for a patient presenting with symptoms suggestive of Helicobacter pylori (H pylori) infection?

Recommended Initial Test for H. pylori Infection

For patients under 50-60 years without alarm symptoms, use either the urea breath test (13C-UBT preferred) or a laboratory-based monoclonal stool antigen test as your first-line diagnostic test—both detect active infection with excellent accuracy (sensitivity 93-97%, specificity 93-95%) and avoid the need for endoscopy. 1, 2

Test Selection Algorithm

For Non-Invasive Testing (Primary Care Setting)

First-line options:

• 13C-Urea Breath Test (13C-UBT): Most accurate non-invasive test with sensitivity 94.7-97% and specificity 95-95.7% 1, 3
• Laboratory-based monoclonal stool antigen test: Comparable accuracy with sensitivity and specificity of approximately 93% 1, 2

Critical advantage: Both tests detect active infection only, unlike serology which cannot distinguish current from past infection 1, 4

When to Proceed Directly to Endoscopy with Invasive Testing

Skip non-invasive testing and perform endoscopy if: 1

• Age ≥50-60 years with new-onset dyspepsia (increased malignancy risk)
• Any alarm symptoms present: bleeding, weight loss, dysphagia, palpable mass, anemia, or malabsorption
• Failed eradication therapy requiring culture and antimicrobial sensitivity testing
• Family history of gastro-oesophageal cancer or from high gastric cancer risk areas

Tests to Avoid

Do NOT use serology as initial diagnostic test: 1, 2

• Overall accuracy only 78% (range 68-82%)—inadequate for clinical use
• Cannot distinguish active infection from past exposure
• Antibodies persist for months to years after eradication
• Particularly problematic: rapid in-office serological tests have even lower accuracy and should be avoided 1

Limited exception for serology: Only consider validated IgG serology when patient recently used PPIs or antibiotics and medication washout is impossible, though this remains suboptimal 1, 2

Critical Pre-Test Preparation

Medication washout periods to avoid false-negatives: 1, 2

• Stop PPIs: At least 2 weeks before testing (causes 10-40% false-negative rates)
• Stop antibiotics and bismuth: At least 4 weeks before testing
• Alternative during washout: H2-receptor antagonists can substitute for PPIs as they don't affect bacterial load 1

For UBT specifically: Patient must fast for at least 6 hours before test for optimal accuracy 2, 3

Test Performance Comparison

The indirect comparison of all four major tests shows statistical differences in accuracy (P = 0.024): 5

At a fixed specificity of 90% with median prevalence of 53.7%:

• 13C-UBT: 94% sensitivity (30 false negatives per 1000 tested)
• 14C-UBT: 92% sensitivity (42 false negatives per 1000 tested)
• Stool antigen: 83% sensitivity (89 false negatives per 1000 tested)
• Serology: 84% sensitivity (86 false negatives per 1000 tested)

Common Pitfalls to Avoid

1. Using rapid in-office immunochromatographic stool tests: These have significantly lower accuracy (80-81%) compared to laboratory-based monoclonal tests—avoid them 2

2. Testing too soon after treatment: For post-eradication confirmation, wait at least 4 weeks after completing therapy 1, 2

3. Using serology for eradication confirmation: Never use serology to confirm eradication as antibodies remain elevated indefinitely 1, 2

4. Inadequate medication washout: Failure to stop PPIs creates false-negatives in all tests except serology 1, 2

5. Wrong patient selection for non-invasive testing: Patients with alarm symptoms or age ≥50-60 years need endoscopy first, not non-invasive testing 1

Special Populations

Safe in all populations: Both UBT (using 13C isotope, not radioactive 14C) and stool antigen test are safe in children and pregnant women 1

Patients with recent GI bleeding: Stool antigen test is technically feasible, though serology may be more reliable in this specific context due to potential low bacterial load 1