## Investigation of Choice for Peptic Ulcer Aetiology ### Clinical Context After acute bleeding is controlled endoscopically, identifying the underlying cause is essential for preventing recurrence. The two major aetiologies of peptic ulcer disease are **H. pylori infection** (60–90% of cases) and **NSAIDs** (10–25%). ### Why H. pylori Testing is the Answer **Key Point:** H. pylori serology and stool antigen are the standard first-line investigations for H. pylori detection in a patient with peptic ulcer disease. **High-Yield:** In India, H. pylori prevalence is 30–40% in the general population and accounts for the majority of peptic ulcer cases. Serology (IgG antibodies) and stool antigen (faecal antigen ELISA) are non-invasive, cost-effective, and sensitive. **Clinical Pearl:** Although endoscopic biopsy (CLO test, histology, or culture) is more specific, it is reserved for cases with alarm features or failed eradication therapy. In a stable patient post-haemostasis, non-invasive serology is preferred as the initial investigation. ### Diagnostic Approach | Investigation | Sensitivity | Specificity | When Used | |---|---|---|---| | **H. pylori serology (IgG)** | 85–95% | 80–90% | First-line, non-invasive | | **Stool antigen** | 90–95% | 95–98% | Non-invasive, good for confirmation | | **Endoscopic biopsy (CLO/histology)** | 95–98% | 98–100% | Gold standard; used if serology negative but suspicion high | | **Fasting gastrin** | — | — | Only if Zollinger–Ellison syndrome suspected (rare) | **Tip:** Always ask about NSAID use (including aspirin) in the history. If NSAIDs are the culprit, H. pylori testing is still performed to guide eradication if co-infected. ### Management Implication If H. pylori is positive, triple or quadruple eradication therapy (PPI + amoxicillin + clarithromycin ± bismuth) is initiated. This reduces ulcer recurrence to <5% if successful eradication is achieved.
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