A 42-year-old man from Delhi presents with a 3-month history of epigastric pain relieved by food and antacids. Upper GI endoscopy reveals a 1.5 cm ulcer on the anterior wall of the first part of the duodenum with clean base. Which investigation is most appropriate to confirm the aetiology of this peptic ulcer?

Explanation

## Investigation of Choice for H. pylori in Peptic Ulcer Disease **Key Point:** The rapid urease test (RUT) on antral mucosa obtained during endoscopy is the gold standard for diagnosing active H. pylori infection in a patient with endoscopically confirmed peptic ulcer. ### Why Rapid Urease Test? The rapid urease test is: - **Sensitivity:** 90–95% (highest among endoscopic tests) - **Specificity:** 95–98% - **Timing:** Results within 1–2 hours - **Cost-effective:** Inexpensive and performed at the bedside - **Direct evidence:** Detects urease enzyme produced by H. pylori in the biopsy specimen ### When to Perform RUT 1. **At the time of endoscopy** — ideal because the patient is already sedated and biopsies are being taken 2. **Multiple biopsies** — take 2–3 samples from antrum (where H. pylori density is highest) to improve sensitivity 3. **Avoid PPI use** — patient should stop PPIs ≥2 weeks before testing (reduces false negatives) ### H. pylori Diagnostic Methods Comparison | Investigation | Sensitivity | Specificity | Timing | Requires Endoscopy | Best Use | |---|---|---|---|---|---| | **Rapid Urease Test** | 90–95% | 95–98% | 1–2 hrs | Yes | Active infection in ulcer disease | | Histology (H&E/IHC) | 95–98% | 98–100% | 24–48 hrs | Yes | Confirmation; assess inflammation | | Faecal Antigen (ELISA) | 90–95% | 93–98% | 24–48 hrs | No | Non-invasive screening; post-treatment | | Serum IgG antibody | 85–95% | 90–95% | 24 hrs | No | Epidemiology; past infection | | Urea Breath Test (UBT) | 95–98% | 95–98% | 20–30 min | No | Gold standard non-invasive; post-Rx | **High-Yield:** In an endoscoped patient with a duodenal ulcer, RUT is the fastest and most practical confirmatory test. ### Clinical Pearl Duodenal ulcers are H. pylori–positive in ~90% of cases (excluding NSAIDs). The anterior wall location is classic for duodenal ulcers and carries risk of perforation. Confirming H. pylori allows targeted eradication therapy. **Mnemonic for H. pylori tests:** **RUSH** = Rapid urease (endoscopic), Urea Breath Test (non-invasive), Serology (IgG), Histology (most specific) ### Rationale Against Other Options - **Serum gastrin:** Used only if Zollinger–Ellison syndrome (ZES) is suspected (multiple ulcers, refractory disease, diarrhoea) — not the first-line test for routine peptic ulcer - **Faecal antigen ELISA:** Non-invasive but less practical in an already-endoscoped patient; better for screening or post-treatment confirmation - **Serum pepsinogen ratio:** Reflects gastric acid secretion and mucosal atrophy; not diagnostic for H. pylori infection [cite:Harrison 21e Ch 297]