Plasma gastrin measurement cannot be used to diagnose a gastrinoma in patients on either proton pump inhibitors or histamine type-2 receptor antagonists

Abstract

Background: Patients with a gastrinoma are treated with proton pump inhibitors (PPI) and histamine type-2 receptor antagonists (H2). In order to diagnose a gastrinoma these drugs must be discontinued, but this increases the risk of gastrointestinal perforation. We aimed to determine if a gastrinoma could be diagnosed without cessation of PPI/H2 therapy. Methods: In all, 90 patients (controls and patients diagnosed with a gastrinoma both on and off PPI/H2 therapy) were recruited, and plasma gastrin measured. Results: Patients with a gastrinoma on PPI/H2 medication had a significantly higher fasting plasma gastrin concentration than control patients on PPI/H2 medication (298±33 versus 204±30 pmol/L, P = 0.01). However, there was substantial overlap between gastrin levels in these two groups. Conclusion: This study confirms that a gastrinoma cannot be diagnosed on the basis of a fasting plasma gastrin assay while patients remain on PPI/H2 therapy.