H. pylori Antibody, IgG
A blood test for antibodies to H. pylori, a common stomach bacterium. A positive result can reflect a past infection, not only a current one.
AI-verified against cited sources. Awaiting expert reviewAlso called HP IgGLOINC 5176-3
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What it is
H. pylori is a common bacterium that lives in the lining of the stomach. Many people never have symptoms, but it can cause gastritis and stomach ulcers. This blood test looks for IgG antibodies, which are proteins your immune system makes after meeting the bacteria. It shows how your immune system has responded, not whether the bacteria are in your stomach right now.
Why it matters
A negative result usually means you did not have an H. pylori infection when your blood was drawn. A positive result is harder to read, because antibodies can stay in the blood for months after an infection has cleared. For this reason, blood tests are not commonly used to diagnose H. pylori today. Stool and breath tests are used to look for a current infection or to check that treatment worked.
If it’s high
A positive result means antibodies to H. pylori were found. The test cannot show whether the bacteria are still in your stomach. Your clinician may suggest a stool or breath test to look for a current infection before deciding on next steps.
Common causes
- A past infection that has cleared or was treated, because antibodies fall slowly over around six months
- A false positive, which is more likely where H. pylori infection is uncommon
- A current H. pylori infection
What can help
- Ask whether a stool antigen or breath test is needed to look for a current infection
- Ask whether your symptoms or history make treatment worth discussing
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 0–0.79 index. Source: Labcorp.
- Adults (this one applies)0–0.79 index
Source: Labcorp
Labcorp H. pylori IgG interpretation (DiaSorin LIAISON assay; lab-specific)
- Negativebelow 0.8 index
- Equivocal0.8 to under 0.9 index
- Positive0.9 and above index
What can affect your result
- Past infection or treatment: antibodies fall slowly after the bacteria are gone
- Kit and cut-off: each lab uses its own kit and scale, and Labcorp reports an index value from a DiaSorin LIAISON assay
- How common H. pylori is where you live: a positive result is less reliable where infection is uncommon
- Local fit of the kit: kits made with bacterial strains from other regions can be less accurate
- Antibodies fall slowly after the bacteria are gone, over around six months, so a positive result can reflect a past infection or one that was treated.
- Each lab uses its own kit, scale and cut-offs, so index values from different labs cannot be compared.
- Kits that use bacterial strains from other parts of the world can be less accurate in your region.
Antibody levels fall slowly, over around six months, after the bacteria are gone, so this test does not show whether treatment worked.
When to talk to a clinician
Get medical help right away for signs of stomach bleeding: black or tarry stool, red blood in vomit or vomit that looks like coffee grounds, sudden or severe belly pain that does not go away, dizziness or fainting, or a rapid pulse. Otherwise, talk with your clinician about a positive result at your next visit.
Questions you could ask
- Why was a blood test chosen instead of a stool or breath test?
- Do I need a stool or breath test to see whether the infection is still active?
- Do my symptoms or history make treatment worth discussing?
Questions people ask
Can this test tell me if I have H. pylori right now?
No. It shows that your immune system has met the bacteria at some point, but antibodies can stay in the blood for months after an infection has cleared. A stool antigen test or a breath test looks for a current infection.
Why is my result an index and not a concentration?
Each lab's kit reports on its own scale, and Labcorp prints an index value with its own cut-offs. The numbers cannot be compared between labs, so look at the lab's own call of negative, equivocal or positive.
I was treated for H. pylori. Can this test show it worked?
No. Antibody levels fall too slowly to show whether the bacteria are gone. Clinicians usually use a stool antigen or breath test for that. Timing matters, because recent antibiotics and acid-reducing medicines can cause false negatives on those tests.
Show the science and sources
For clinicians and researchers
IgG against H. pylori is usually measured by ELISA or, at Labcorp, by a chemiluminescence immunoassay (DiaSorin LIAISON) reported as an index value with negative below 0.80, equivocal 0.80–0.89 and positive above 0.89. Serology does not distinguish active from past infection. IgG titers decline slowly, over around six months, so the test is not recommended to confirm eradication. The positive predictive value depends on local prevalence and falls where prevalence is under about 20%. Kits should be validated locally, especially when the antigen strains come from other regions. In a review of 99 studies against histology, serology had a sensitivity of about 84% at a specificity of 90%, compared with 94% for the 13C urea breath test and 83% for stool antigen. The urea breath test and the monoclonal stool antigen test are the preferred non-invasive tests of active infection, both for the first diagnosis and after treatment when endoscopy is not needed. The 2024 ACG guideline on H. pylori addresses who should be tested and whether every treated patient needs a test of cure. Labcorp reports this test under LOINC 5176-3, while 7902-0 is a broader units-per-volume code.
LOINC 5176-3 (primary), 7902-0, 17859-0, 16126-5. Specimen: serum.
Sources
- H. pylori, IgG Abs (test 162289), Labcorp
- Helicobacter pylori (H. pylori) Tests, MedlinePlus Medical Tests (National Library of Medicine)
- What Is New in Helicobacter pylori Diagnosis. An Overview, Journal of Clinical Medicine (2021)
- ACG Clinical Guideline: Treatment of Helicobacter pylori Infection, American Journal of Gastroenterology (2024)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.