H. pylori Antigen vs Antibody Test
Direct answer: The stool antigen test detects H. pylori antigen and indicates active infection (and works for test-of-cure); the antibody test detects immune exposure and cannot distinguish active from past infection.
Comparison table
| Stool antigen | Antibody (serology) | |
|---|---|---|
| Detects | H. pylori antigen in stool | Anti-H. pylori antibodies |
| Indicates | Active infection | Exposure (current or past) |
| Test-of-cure | Yes (after eradication) | No (stays positive) |
| Specimen | Stool | Whole blood / serum / plasma |
What each test detects
- Stool antigen: bacterial antigen shed in stool during active colonization.
- Antibody: immune response that persists after the infection clears.
Strengths
- Stool antigen: detects active infection, suitable for test-and-treat and post-treatment confirmation.
- Antibody: cheap, widely available; useful where endoscopy/stool testing is unavailable.
Limitations
- Stool antigen: PPI or antibiotic use can suppress detection (false negative).
- Antibody: cannot confirm active infection or eradication.
False negative / positive considerations
- Stool antigen false negative: recent PPI/antibiotics.
- Antibody false positive: persistent antibodies from past infection.
Confirmatory testing
Urea breath test or endoscopy with biopsy is the reference; stool antigen is a non-invasive alternative.
Procurement considerations
For clinics running test-and-treat, stool antigen is the preferred rapid option; serology suits low-resource screening.
Related pages
Which test to choose
Choose the stool antigen test for active infection and test-of-cure; use serology only where stool testing is unavailable, as it cannot distinguish active from past infection.
Last reviewed: 2026-09-12