How do I retest for Helicobacter pylori (H. pylori) infection after completing antibiotic treatment?

How to Retest for H. pylori After Antibiotic Treatment

Use a urea breath test (UBT) or validated monoclonal stool antigen test at least 4 weeks after completing treatment, ensuring patients have stopped proton pump inhibitors for 2 weeks and antibiotics/bismuth for 4 weeks before testing. 1, 2

Timing of Retesting

Wait at least 4 weeks after treatment completion before performing any test of cure to allow adequate gastric mucosal recovery and avoid false-negative results from temporary bacterial suppression rather than true eradication. 1, 2

• In bleeding peptic ulcer cases specifically, consider delaying testing to 4-8 weeks after the bleeding episode. 2
• Testing before 4 weeks will yield unreliable results as the gastric mucosa requires this recovery period. 2

Recommended Testing Methods

First-Line Non-Invasive Tests

Urea Breath Test (UBT) is the gold standard for confirming eradication with sensitivity of 94.7-97% and specificity of 95-100%. 1, 2

Validated monoclonal stool antigen test is an equally accurate alternative with sensitivity and specificity >90%, particularly useful when patients must continue PPI therapy. 1, 2

When to Use Endoscopy-Based Testing

Endoscopy with biopsy is mandatory in specific high-risk scenarios: 1, 2

• Gastric ulcer patients require endoscopic follow-up to ensure complete healing and exclude malignancy, as some gastric cancers are only detected during the healing process. 1
• Gastric MALT lymphoma cases need endoscopy with biopsies from both antrum and body to assess tumor regression. 1, 2
• Complicated peptic ulcer disease (bleeding, perforation) warrants endoscopic confirmation. 1

Critical Pre-Test Medication Washout

Failure to properly discontinue medications is a common cause of false-negative results. Follow these specific washout periods: 1, 2, 3

• Antibiotics and bismuth: Stop for at least 4 weeks before testing 1, 2, 3
• Proton pump inhibitors (PPIs): Stop for at least 2 weeks (preferably 7-14 days) before testing 1, 2, 3
• Fasting: Patients must fast for at least 6 hours before UBT 2, 3

Important caveat: Histamine-2 receptor antagonists do not affect bacterial load and can be substituted for PPIs during the washout period. 1

What NOT to Use for Retesting

Serology has absolutely no role in determining eradication success because antibodies remain positive long after infection is cleared (serologic "scar"), making it impossible to distinguish active infection from past exposure. 1, 2

Interpreting Results and Next Steps

If Test Remains Positive (Treatment Failure)

After confirmed treatment failure, never repeat the same antibiotic regimen—this leads to further resistance. 1, 2

• After first failure: Use a completely different antibiotic combination, avoiding any antibiotics used in the initial regimen. 1, 2
• After second failure: Pursue antimicrobial susceptibility testing whenever possible to guide third-line therapy. 1, 2
• Avoid clarithromycin if there is any history of macrolide exposure (azithromycin, clarithromycin). 1, 2
• Avoid levofloxacin if there is any history of fluoroquinolone use. 1, 2

If Test is Negative (Successful Eradication)

• Uncomplicated duodenal ulcer: No further PPI therapy needed after confirmed eradication. 2
• Gastric ulcer: Continue PPI until complete healing is confirmed endoscopically. 2
• Complicated ulcers: Continue PPI until eradication is confirmed. 2

Common Pitfalls to Avoid

Testing too early (before 4 weeks) is the most common error, yielding false-negative results that lead to inappropriate reassurance. 1, 2

Inadequate medication washout causes false-negative results—verify that patients have actually stopped PPIs, antibiotics, and bismuth for the required periods. 1, 2

Using serology for test of cure is completely inappropriate and will lead to incorrect clinical decisions. 1, 2

False-positive UBT results can occur in patients with achlorhydria (pernicious anemia, atrophic gastritis) due to overgrowth of non-H. pylori urease-producing organisms. If false-positive results are suspected after repeated treatment failures, confirm with stool antigen test or endoscopy before giving another course of therapy. 1

Positive results can always be trusted—medications that decrease bacterial load produce false-negative tests, not false-positive tests. 1