What is an H. pylori Antigen test?
The H. pylori Antigen test is a stool test that detects antigens (proteins) from Helicobacter pylori bacteria in a stool sample.
H. pylori is a bacterium that can infect the stomach and is a common cause of gastritis and peptic ulcers. If left untreated, persistent infection can increase the risk of certain stomach complications.
Unlike blood antibody testing, which may remain positive after an infection has been treated, the stool antigen test is useful for detecting current H. pylori infection.
What is the H. pylori Antigen test used for?
The test is used to:
Detect an active H. pylori infection
Help investigate symptoms associated with gastritis or peptic ulcer disease
Support the diagnosis of H. pylori-related stomach problems
Confirm that H. pylori has been successfully eliminated after treatment
The stool antigen test may also be used in children and adults when testing for active infection is appropriate.
Why do I need an H. pylori Antigen test?
Your healthcare provider may recommend this test if you have symptoms such as:
Upper abdominal pain or discomfort
Burning or aching stomach pain
Bloating
Nausea
Frequent belching
Indigestion
Loss of appetite
Recurrent stomach symptoms
The test may also be requested if you have a history of peptic ulcer disease or if your healthcare provider wants to confirm that H. pylori treatment has been successful.
What happens during the test?
You will need to provide a small stool sample in a clean, dry container provided or approved by the laboratory.
The sample is tested using an immunological method that detects H. pylori antigens.
Avoid mixing the stool sample with urine, water, toilet disinfectants, or other substances, as contamination can interfere with the test.
Will I need to do anything to prepare?
Usually, fasting is not required.
However, some medications can reduce the amount of H. pylori in the stomach and may cause a false-negative result. These include:
Antibiotics
Bismuth-containing medications
Proton pump inhibitors (PPIs) such as omeprazole, esomeprazole, pantoprazole, or lansoprazole
For reliable testing, your healthcare provider may recommend stopping PPIs for approximately 2 weeks and antibiotics or bismuth-containing medications for approximately 4 weeks before testing, when medically appropriate.
Do not stop prescribed medications without consulting your healthcare provider.
Are there any risks?
There are no significant medical risks associated with collecting a stool sample.
The main consideration is obtaining a clean, uncontaminated specimen and following the laboratory's collection instructions.
What do the results mean?
Positive result
A positive result means that H. pylori antigen was detected in the stool.
This is consistent with a current H. pylori infection, particularly when the patient has compatible symptoms or clinical findings.
Your healthcare provider may recommend eradication treatment, usually involving a combination of antibiotics and acid-suppressing medication according to the appropriate treatment regimen.
Negative result
A negative result means that H. pylori antigen was not detected in the stool.
This generally suggests that an active H. pylori infection is unlikely.
However, a false-negative result can occur, particularly if the patient has recently taken antibiotics, bismuth, or proton pump inhibitors.
If symptoms continue despite a negative result, your healthcare provider may recommend repeat testing or another method, such as a urea breath test.
Important note about the results
The H. pylori Stool Antigen test is a useful test for detecting active H. pylori infection and can also be used to confirm eradication after treatment.
For post-treatment testing, testing should generally be performed at least 4 weeks after completing antibiotics and after an appropriate period off proton pump inhibitors, because these medications can suppress H. pylori and produce false-negative results.
A negative result obtained while taking interfering medications may not reliably exclude infection.
Results should always be interpreted together with the patient's symptoms, medical history, previous treatment, medication use, and the laboratory's validated test method and reference criteria.
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