## **Core Concept**
The question tests the understanding of diagnostic methods for confirming Helicobacter pylori (H. pylori) eradication. H. pylori is a bacterium that infects the stomach lining and can cause peptic ulcers and gastric cancer. Confirming eradication is crucial to ensure the effectiveness of treatment.

## **Why the Correct Answer is Right**
The correct answer, **Urea Breath Test (UBT)**, is a widely used non-invasive test to confirm H. pylori eradication. UBT measures the activity of urease, an enzyme produced by H. pylori. The test involves ingesting a small amount of radioactive or non-radioactive urea. If H. pylori is present, the urease breaks down the urea into carbon dioxide and ammonia. The labeled carbon dioxide is then exhaled and can be detected in the breath. A negative result indicates the absence of H. pylori or successful eradication.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Stool antigen test can be used to diagnose H. pylori infection but is not the most reliable test for confirming eradication due to potential false positives from residual antigen.
- **Option B:** Endoscopy with biopsy is an invasive method that can be used to diagnose H. pylori infection but is not typically used for confirming eradication due to its invasive nature and cost.
- **Option D:** Blood test for H. pylori antibodies is not useful for confirming eradication because antibodies can persist in the blood for months to years after successful treatment.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **Urea Breath Test (UBT)** and **Stool Antigen Test** are preferred for confirming H. pylori eradication, with UBT being particularly favored for its high sensitivity and specificity. It's also important to wait at least 4 weeks after completing antibiotic treatment and 2 weeks after completing proton pump inhibitor (PPI) therapy before performing a confirmatory test.

## **Correct Answer:** C. Urea Breath Test.