Preparations Required Before H. pylori Stool Antigen Test
Stop proton pump inhibitors (PPIs) for 2 weeks before performing the H. pylori stool antigen test to avoid false-negative results. 1
Medication Discontinuation Requirements
Proton Pump Inhibitors (PPIs)
- Discontinue PPIs at least 2 weeks prior to testing (Evidence level: 1b, Grade of recommendation: A) 1
- PPIs increase gastric pH, which decreases H. pylori bacterial load in the stomach (especially in the antrum), leading to 10-40% false-negative rates across diagnostic tests including stool antigen testing 1
- This 2-week washout period allows bacteria to repopulate the stomach and restores test accuracy 2
- Be vigilant about over-the-counter PPI use, as patients with dyspeptic symptoms commonly self-medicate with these readily available medications 2
Antibiotics and Bismuth Products
- Stop antibiotics and bismuth-containing products for at least 2 weeks before testing 1
- These medications directly reduce bacterial load and cause false-negative results 1
H2-Receptor Antagonists
- H2-receptor antagonists (like famotidine) may cause false-negative results but to a much lesser extent than PPIs 1
- While the Maastricht IV/Florence Consensus did not mandate stopping H2 blockers, a 2-week discontinuation is prudent if clinically feasible 3
Alternative Testing Strategy If Medications Cannot Be Stopped
- If stopping PPIs or other interfering medications is not possible, use validated IgG serology instead (Evidence level: 2b, Grade of recommendation: B) 1
- Serology is the only test unaffected by medications that reduce bacterial load, as antibodies remain elevated despite transient decreases in H. pylori 1
- Only use validated commercial serological tests with accuracy >90%; avoid rapid in-office tests with limited accuracy 3
Critical Clinical Pitfalls to Avoid
- A positive stool antigen test can be trusted even during PPI therapy, as these medications cause false-negative results, not false-positive results 1
- If uncertain about a negative result in a patient on interfering medications, repeat the test after an appropriate washout period (at least 2 weeks) rather than accepting the negative result 1
- The washout period after long-term PPI treatment has not been formally studied, so consider extending beyond 2 weeks for patients on chronic therapy 1
No Other Special Preparations Required
- Unlike some diagnostic tests, the stool antigen test requires no dietary restrictions, fasting, or other special preparations beyond medication discontinuation 4, 5
- Simply collect a stool sample after the appropriate medication washout period 4, 5
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