Infection Tests

H. pylori Testing

Also written as: Helicobacter pylori test, Urea breath test, H. pylori stool antigen, H. pylori antibody

Checks for H. pylori, a stomach bacterium linked to ulcers, using breath, stool, or blood methods.

What it measures

Evidence of Helicobacter pylori, a bacterium that can live in the stomach lining. The breath test detects a gas the bacterium produces from a swallowed test substance, the stool test detects fragments of the bacterium itself, and the blood test detects antibodies the immune system has made against it.

Why a doctor orders it

Ordered when persistent indigestion, stomach pain, or ulcers are being evaluated, because this bacterium is a common and treatable cause. Breath or stool testing is also used after treatment to confirm the bacterium is gone.

What is generally associated with a higher result

In general terms, a positive breath or stool test generally reflects a current, active infection, because both depend on the living bacterium being present. A positive blood antibody indicates exposure at some point, but it can stay positive for years after the bacterium has been cleared, so it does not reliably separate past infection from present infection.

What is generally associated with a lower result

A negative breath or stool test generally indicates no active infection, though certain common stomach medicines and recent antibiotics can suppress the bacterium enough to produce a falsely negative result. A negative blood antibody generally indicates no evidence of exposure.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

• Acid-reducing medicines such as proton pump inhibitors, which can cause false negatives on breath and stool tests
• Recent antibiotics or bismuth-containing stomach remedies, which can also mask an active infection
• Not fasting as instructed before a breath test
• A previously treated infection, after which the blood antibody can remain positive for years
• Delays or handling problems with a stool sample reaching the lab

Questions to take to your appointment

• Was mine a breath, stool, or blood test, and does that change what the result can show?
• Could any of my current medicines, such as acid reducers, have affected the accuracy?
• If treatment is given, which test would later confirm the bacterium is actually gone?
• Do my symptoms fit what this bacterium typically causes, or should something else be considered?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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