H. pylori Testing: Stool Antigen vs Breath Test vs Blood Antibody

Helicobacter pylori infects roughly a third of US adults and most carriers never have symptoms. Testing is worthwhile when there is a reason to treat a positive result — guidelines from the American College of Gastroenterology recommend testing (and treating if positive) for:

• Persistent upper-abdominal burning or gnawing pain, especially between meals or at night, or recurring indigestion under age 60 without red-flag symptoms
• A current or past stomach or duodenal ulcer, or a history of stomach cancer in a first-degree relative
• Unexplained iron-deficiency anemia or low ferritin once other causes are excluded
• Long-term daily aspirin or NSAID use, where H. pylori multiplies the ulcer risk
• Immune thrombocytopenia (low platelets) — eradication sometimes raises the count
• A household member who tested positive, if you have symptoms

Testing without a plan to treat is not recommended — a positive result should be followed by a 14-day antibiotic-based regimen from a clinician, then a test of cure.

Stool antigen test. Detects H. pylori protein in a stool sample, which only happens when live bacteria are present. Sensitivity and specificity are both about 94% with monoclonal assays. It works for diagnosis and for confirming eradication, and it is the easiest to collect — a small sample in the kit the lab provides, no fasting.

Urea breath test (UBT). You drink a solution of labeled urea; H. pylori's urease enzyme splits it and the labeled carbon appears in your breath within 15–30 minutes. Sensitivity and specificity are about 95%. It's performed at the lab, needs a 1-hour fast and no smoking beforehand, and — like the stool test — reflects active infection.

Blood antibody (IgG) test. Measures your immune response to the bacterium. The problem: antibodies persist for months to years after the infection is gone, so a positive result cannot distinguish a current infection from one treated a decade ago, and the test cannot be used to confirm cure. Guidelines now discourage it except where stool and breath testing aren't possible. TestWell's H. pylori offerings are stool-antigen and breath-based for this reason.

Test	Detects active infection?	Use for test-of-cure?	Affected by PPIs / antibiotics?	Sample
Stool antigen	Yes	Yes	Yes — stop first	Stool, collected at home or lab
Urea breath test	Yes	Yes	Yes — stop first	Breath, in-lab, 1-hour fast
Blood IgG antibody	Can't tell past from present	No	No	Blood

Stool and breath tests look for live, active bacteria, so anything that suppresses H. pylori temporarily can produce a false negative:

• Proton-pump inhibitors (omeprazole, esomeprazole, pantoprazole, lansoprazole): stop for 2 weeks before the sample. Famotidine (Pepcid) and antacids like Tums are fine to use in the meantime and don't affect the test.
• Antibiotics and bismuth (Pepto-Bismol): stop for 4 weeks before testing.
• For the breath test: nothing to eat or drink for 1 hour before, no smoking.
• For the stool test: no special diet; collect the sample per the kit instructions and return it promptly.

If you cannot stop a PPI for two weeks — some people with severe reflux can't — tell the clinician who reviews your results; a positive test is still reliable, but a negative one is less certain.

A positive stool antigen or breath test means an active infection. Because H. pylori causes most ulcers and is a WHO class 1 carcinogen for stomach cancer, the standard advice is to treat every confirmed infection — usually 14 days of two antibiotics plus a PPI, sometimes with bismuth. Treatment needs a prescription, so bring the result to a clinician or use a telehealth visit.

Test of cure. Because first-line treatment fails 10–20% of the time (largely antibiotic resistance), guidelines recommend confirming eradication in everyone treated. Retest with a stool antigen or breath test at least 4 weeks after finishing antibiotics and after 2 weeks off PPIs. Never use the blood antibody test for this — it will still be positive.

A negative result with persistent symptoms points elsewhere: acid reflux, functional dyspepsia, gallbladder disease, celiac disease or medication side effects. Alarm features — trouble swallowing, vomiting, weight loss, black or bloody stools, a new problem after age 60 — warrant an endoscopy rather than another stool test.