Hypochlorhydria and achlorhydria are associated with false-positive secretin stimulation testing for Zollinger-Ellison syndrome.

OBJECTIVES Secretin stimulation testing (SST) is used to evaluate patients with hypergastrinemia in the diagnosis of Zollinger-Ellison syndrome. Case series have documented false-positive SST in patients with achlorhydria. This study reviews our experience with SST in hypochlorhydric and achlorhydric patients. METHODS We examined 27 patients with hypochlorhydria or achlorhydria based on a predefined basal acid output (BAO) measurement of less than 5.0 mEq/h who also underwent SST for diagnosis of Zollinger-Ellison syndrome. We report the frequency of false-positive SST results in this setting. RESULTS Three hundred thirty patients underwent gastric analysis of which 27 had BAO of less than 5.0 mEq/h and SST conducted. The mean (SD) fasting gastrin level was 247 (304) pg/mL, and the mean (SD) BAO measurement was 1.6 (1.8) mEq/h. Twenty patients were off, and 7 were on antisecretory therapy at time of testing. Four patients had false-positive SST results: 3 with gastric atrophy (BAO = 0 mEq/h) and 1 with drug-induced hypochlorhydria (BAO = 0.5 mEq/hr). These false-positive test results were confirmed by structural and functional imaging studies. CONCLUSIONS We have identified a 14.8% false-positive rate in SST in patients with hypochlorhydria or achlorhydria. Growing literature has identified severe consequences associated with discontinuing antisecretory treatment for testing; therefore, SST will require interpretation in the setting of gastric acid suppression and needs to be interpreted in this context.