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Helicobacter Antigen in Stool

Bacterial infections Biomarker

Sample Needed

Collection Type: Stool

Body System

Related System: Bacterial infections

Overview

The Helicobacter pylori (H. pylori) stool antigen test detects proteins (antigens) from H. pylori bacteria in a fecal sample, showing current active infection in the stomach lining. It is a non‑invasive alternative to breath testing or endoscopic biopsy culture and is used to diagnose H. pylori–related gastritis, peptic ulcer disease, unexplained iron‑deficiency anemia, or suspected MALT lymphoma risk. Symptoms prompting testing include persistent epigastric pain, dyspepsia, nausea, bloating, unexplained gastrointestinal bleeding or recurrent ulcers. Test performance can vary by age and geography because prevalence is higher in older adults and in regions with greater endemic rates; recent use of proton‑pump inhibitors, antibiotics or bismuth reduces sensitivity and may yield false negatives. Gender has minimal direct effect on test accuracy.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Bacterial infections - Symptoms: persistent upper abdominal pain, dyspepsia, nausea, unexplained iron‑deficiency anemia, history of peptic ulcer or GI bleeding - Diagnoses/monitoring: detects active H.
pylori infection; used to confirm eradication after therapy - Reasons for abnormal (positive) result: active H.
pylori colonization of the stomach - Biological meaning: antigen presence indicates ongoing bacterial shedding into stool - Behaviors/lifestyle causing abnormal results: recent antibiotic, bismuth, or PPI use can cause false‑negative results; poor sample handling can affect accuracy - Family history: relatives with peptic ulcer disease or gastric cancer increases need for testing

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Understanding Test Results

Index <0.9 or a reported "Negative" no H.
pylori antigen detected; suggests absence of active infection or successful eradication.
Consider timing and medication effects if clinical suspicion remains.
Index 0.9–1.1 (equivocal/gray zone) indeterminate; repeat testing on a new stool sample or perform an alternative test (urea breath test or endoscopy) after appropriate washout from PPIs/antibiotics.
Index >1.1 or a reported "Positive" H.
pylori antigen detected; indicates active infection and warrants treatment or further clinical evaluation.
False positives are uncommon but can occur shortly after treatment; avoid testing for test‑of‑cure until at least 4 weeks after completing antibiotics and at least 2 weeks after stopping PPIs (longer intervals may be recommended depending on clinical context).
Low/negative results in symptomatic patients may reflect recent medication interference, low bacterial load, poor specimen quality, or non‑H.
pylori causes of symptoms.

Normal Range

Index <0.9 (unitless) OR Negative (qualitative stool antigen)

FAQs

Q: What does it mean when H. pylori antigen is positive in stool?

A: A positive Helicobacter pylori stool antigen means H. pylori proteins were detected in your feces, indicating an active stomach infection. It’s used to diagnose current infection and to confirm eradication after treatment. Results can be affected by recent antibiotics, bismuth, or proton‑pump inhibitors, so your doctor may repeat testing or recommend appropriate eradication therapy (usually combination antibiotics plus acid suppression).

Q: What happens if Helicobacter pylori is positive?

A: If testing is positive for Helicobacter pylori, it means a stomach infection that can cause chronic gastritis, peptic ulcers and dyspepsia; many people have no symptoms. Untreated infection can lead to ulcer complications (bleeding, perforation) and a small long-term increased risk of gastric cancer and MALT lymphoma. Treatment is combination antibiotics plus acid suppression, with a follow-up test to confirm eradication.

Q: How to treat H. pylori in pregnancy?

A: In pregnancy, H. pylori eradication is usually postponed until after delivery unless there’s a complicated ulcer or severe symptoms. If treatment is necessary, clinicians prefer a PPI plus amoxicillin (safest); metronidazole may be added if needed. Avoid tetracyclines and generally avoid clarithromycin if possible. Always consult your obstetrician or gastroenterologist to weigh risks and choose timing and drugs.

Q: Can Helicobacter cause poop problems?

A: Helicobacter pylori primarily infects the stomach and causes gastritis, ulcers, indigestion, nausea, bloating and sometimes loss of appetite. It does not usually produce major changes in bowel movements, but some people may experience diarrhea or constipation. Ulcer-related bleeding can cause black, tarry stools. If you have persistent stool changes, blood in stool, fever or weight loss, see a doctor for testing and treatment.

Q: What foods should I avoid with H. pylori?

A: Avoid foods that irritate the stomach and promote acid: spicy dishes, high‑fat and fried foods, very acidic items (citrus, tomatoes), and carbonated drinks. Cut back on smoked, pickled, salty or processed foods and sugary junk food. Also limit alcohol, coffee/caffeinated drinks and smoking, which worsen symptoms and delay healing. Eat bland, low‑fat, minimally processed meals instead.

Q: How long does H. pylori stay positive after treatment?

A: Urea breath and stool antigen tests usually become negative about 4 weeks after completing antibiotics; also stop proton‑pump inhibitors for at least 2 weeks before testing. Serological (antibody) tests often remain positive for many months to years, so they aren’t useful for confirming eradication. If symptoms continue, repeat testing with breath or stool antigen after the recommended waiting period.