What laboratory tests do you order to diagnose H. pylori (Helicobacter pylori) infection?

Laboratory Tests for H. pylori Diagnosis

Order either a urea breath test (UBT) or a laboratory-based monoclonal stool antigen test as your first-line non-invasive diagnostic test for H. pylori infection. 1, 2

Preferred Non-Invasive Tests

Urea Breath Test (UBT)

• UBT is the most accurate non-invasive test available, with sensitivity of 94-97% and specificity of 95-97.7% 1, 2
• Detects active infection by measuring urease activity produced by live H. pylori bacteria 1
• Requires patient to fast for at least 6 hours before testing 2
• Use 13C-urea (non-radioactive) for all populations including children and pregnant women 3

Stool Antigen Test

• Use only laboratory-based monoclonal antibody stool antigen tests, which achieve sensitivity and specificity of approximately 93% 1, 2, 3
• Directly detects H. pylori bacterial antigens in stool specimens 2
• Comparable accuracy to UBT for both initial diagnosis and post-treatment confirmation 1, 3
• Avoid rapid in-office immunochromatographic stool tests - these have significantly lower accuracy (limited to 80-81%) and should not be used 4, 3

When to Use Invasive Tests (Endoscopy Required)

Order endoscopy with biopsy-based testing for:

• Patients ≥50 years with new-onset dyspepsia 1
• Any patient with alarm symptoms (bleeding, weight loss, dysphagia, palpable mass) 1, 2
• Patients who have failed eradication therapy and need antimicrobial susceptibility testing 1, 2

Invasive Test Options During Endoscopy

• Rapid urease test (RUT): 80-95% sensitivity, 95-100% specificity, provides quick results 1, 2
• Histology: Requires at least two biopsies from antrum and body; immunohistochemistry is the gold standard 1, 2
• Culture: Allows antimicrobial susceptibility testing, particularly valuable after treatment failure 1, 2

What NOT to Order

Serology (IgG Antibody Tests)

• Do not use serology for routine diagnosis - overall accuracy averages only 78% (range 68-82%) 4, 2, 3
• Cannot distinguish active infection from past exposure; antibodies persist for months to years after eradication 4, 2, 3
• Never use serology to confirm eradication 2, 3
• Only consider validated IgG serology when patient has recently used PPIs or antibiotics and you cannot wait for medication washout 4, 3

Critical Testing Pitfalls to Avoid

Medication Washout Requirements

• Stop proton pump inhibitors (PPIs) at least 2 weeks before testing with UBT, stool antigen, RUT, histology, or culture 1, 2, 3
• Stop antibiotics and bismuth at least 4 weeks before testing 1, 2, 3
• Failure to observe these washout periods causes false-negative results in all tests except serology 2, 3
• H2-receptor antagonists do not affect bacterial load and can substitute for PPIs when acid suppression is needed before testing 3

Confirmation of Eradication Testing

• Test no earlier than 4 weeks after completing treatment 1, 2, 3
• Use UBT or laboratory-based monoclonal stool antigen test only 1, 2
• Never use serology for post-treatment confirmation 2, 3

Practical Algorithm

For young patients (<50 years) without alarm symptoms:

• Order UBT or laboratory-based monoclonal stool antigen test 1, 2
• Ensure proper medication washout (PPIs 2 weeks, antibiotics 4 weeks) 1, 2
• If recent medication use prevents washout and clinical suspicion is high, consider validated IgG serology 4, 3

For patients ≥50 years or with alarm symptoms:

• Refer for endoscopy with RUT, histology, or culture 1, 2
• Consider culture specifically if antimicrobial resistance is suspected 1, 2