Which test is most reliable for confirming eradication of H. pylori after therapy?

• A. EGD
• B. Serologic testing
• C. Stool antigen test
• D. Urea breath test

Answer: (D)

The key idea is to use a test that shows active infection rather than past exposure. After H. pylori therapy, you want to know if the bacteria are still present, not just whether antibodies exist. The urea breath test does exactly that: it detects active urease activity in the stomach. Ingested labeled urea is split by any live H. pylori urease, and the labeled CO2 exhaled in the breath reveals ongoing infection. Because it directly reflects current bacterial activity, it has high sensitivity and specificity and is noninvasive, making it the preferred confirmatory test after treatment.

Serologic testing looks for antibodies, which can persist long after eradication, so a positive serology doesn’t reliably distinguish current infection from a past one. Endoscopy with biopsy and rapid urease testing is invasive and generally reserved for persistent symptoms or complications rather than routine check after therapy. The stool antigen test is reliable and noninvasive as well, but the urea breath test tends to have the best combination of accuracy and practicality in many settings, especially when obtained after an appropriate washout period.

To minimize false results, wait until about 4 weeks after completing therapy and keep PPIs stopped for about 2 weeks (and antibiotics for longer per guidelines) before testing. If negative, eradication is likely; if positive, further evaluation and retreatment may be needed.