What is the recommended method for diagnosing H (Helicobacter) pylori infection?

H. pylori Diagnosis

For diagnosing active H. pylori infection, use the urea breath test (UBT) or stool antigen test as first-line non-invasive methods, with UBT demonstrating the highest accuracy (sensitivity 94-97%, specificity 95%) and both tests being superior to serology for detecting current infection. 1, 2

Recommended Non-Invasive Tests (First-Line)

Urea Breath Test (UBT)

• The UBT is the most accurate non-invasive diagnostic test available, detecting active infection by measuring urease activity of H. pylori in the stomach 1, 2
• Requires patients to fast for at least 6 hours before testing for optimal accuracy 1, 2
• Sensitivity ranges from 94-97% with specificity of 95% 1, 2
• Recommended by the American College of Gastroenterology as a primary diagnostic test 1
• Useful for both initial diagnosis and post-treatment confirmation of eradication 2

Stool Antigen Test

• Directly detects H. pylori bacterial antigens in stool specimens with sensitivity and specificity of approximately 93%, making it comparable to UBT 1, 3
• A laboratory-based validated monoclonal stool antigen test is specifically recommended over rapid in-office immunochromatographic tests (which have lower accuracy of 80-81%) 1
• Excellent alternative for both initial diagnosis and post-treatment confirmation 1, 3
• More practical than invasive methods, avoiding endoscopy-related discomfort, expense, and complications 3
• The European Helicobacter Pylori Study Group recommends either UBT or stool antigen test for initial diagnosis 3

Tests NOT Recommended for Routine Diagnosis

Serology (IgG Antibody Tests)

• Do not use serological tests for confirming active infection or for post-eradication testing 1
• Cannot distinguish between active infection and past exposure, as antibodies persist for months to years after eradication 1
• Overall accuracy of commercial ELISA serology tests averages only 78% (range 68-82%) 4, 1
• The American Gastroenterological Association advises against using serology for routine diagnosis 1
• May be considered only when patients have recently used proton pump inhibitors or antibiotics and medication washout is not possible 1

Invasive Tests (When Endoscopy is Performed)

Histological Examination

• Considered a gold standard among invasive tests, requiring at least two biopsy samples from both antrum and body for improved sensitivity 1
• Immunohistochemistry is the established gold standard for histology with high sensitivity and specificity 1
• Provides additional information about gastric inflammatory mucosal lesions and precancerous changes 5

Rapid Urease Test (RUT)

• Pre-treatment sensitivity ranges from 80-95% with specificity of 95-100% 1
• Requires approximately 10^4 organisms for a positive result 1
• Less sensitive than histology but highly specific 5

Culture

• Provides definitive proof of infection and allows antimicrobial susceptibility testing 1
• Particularly valuable after treatment failure when antimicrobial resistance is suspected 1
• Technically demanding with variable sensitivity between laboratories 1

Critical Testing Considerations to Avoid False Results

Medication Washout Requirements

• Proton pump inhibitors must be discontinued at least 2 weeks before testing 1, 3
• Antibiotics must be discontinued at least 4 weeks before testing 1
• Bismuth compounds should also be discontinued before testing 1, 3
• These medications cause false-negative results with all diagnostic tests 1

Post-Treatment Confirmation

• Testing for eradication should be performed no earlier than 4 weeks after completion of treatment 1
• Use UBT or stool antigen test for confirmation, never serology 1
• If endoscopic control is necessary after treatment failure, combine biopsy culture with antibiotic susceptibility testing and histology 5

Clinical Algorithm for Test Selection

For young patients (<45-55 years) with uncomplicated dyspepsia and no alarm symptoms (anemia, weight loss, dysphagia, melena):

• Use "test and treat" strategy with UBT or stool antigen test 4, 1
• This approach reduces total endoscopies by 62% compared to prompt endoscopy 4

For patients with alarm symptoms or age >45-55 years:

• Refer for endoscopy with invasive testing (histology, RUT, culture if needed) 4

For post-treatment confirmation:

• Use UBT or stool antigen test at least 4 weeks after treatment completion 1

When recent PPI/antibiotic use cannot be avoided:

• Consider validated IgG serology as the only acceptable alternative 1