Zollinger-Ellison syndrome (ZES) is caused by a gastrinoma. The most sensitive biochemical test for confirming the diagnosis when fasting serum gastrin is borderline elevated (150–500 pg/mL) and gastric pH <2 is:
- A Secretin stimulation test (positive if gastrin rises >120 pg/mL above baseline) ✓
- B Calcium infusion test
- C Meal stimulation test
- D Pentagastrin stimulation test
Correct answer: A. Secretin stimulation test (positive if gastrin rises >120 pg/mL above baseline)
Explanation
The secretin stimulation test is the confirmatory gold standard for ZES. In normal subjects, secretin suppresses gastrin; in gastrinoma, secretin paradoxically stimulates gastrin release. A positive test is defined as an increase in serum gastrin >120 pg/mL (or >200 pg/mL in some definitions) above baseline following IV secretin. This differentiates ZES from other causes of hypergastrinaemia (e.g., atrophic gastritis, PPI use).
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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