Sensitivity, specificity and predictive values of the secretin infusion test in the diagnosis of gastrinoma

From 1974 to 1981, 55 patients, 18 with Zollinger-Ellison syndrome (ZES) histologically confirmed and 37 patients with duodenal ulcer (DU) without pylorostenosis were followed for a minimal period of 5 years. The diagnostic values of a) basal acid output (BAO mEq/h); b) 60 min acid output after secretin infusion, 3 CU-GIH/kg, (MAO-SE mEq/h); c) basal serum gastrin (BSG pg/ml: mean of 4 gastrin determinations) and d) serum gastrin after secretin (SG-SE pg/ml: mean of 4 gastrin determinations during secretin infusion) were calculated. Cut off point values of 100 p. 100 specificity (i. e. no DU patient reached these values) with a positive predictive value of 100 p. 100 (i. e. probability for gastrinoma when this cut off point was attained) were BAO greater than 26 mEq/h, MAO-SE greater than 18 mEq/h, BSG greater than 221 pg/ml, SG-SE greater than 186 pg/ml. The sensitivities of these parameters (i. e. percent of ZES which reached the given cut off point) were respectively (p. 100): 39, 78, 72 and 94. Ranking these parameters according to their own discriminative value expressed by R2 (square correlation coefficient) gave SG-SE, R2 = 0.559; BSG, R2 = 0.508; MAO-SE, R2 = 0.456; BAO, R2 = 0.414. The most discriminative association of 2 variables was SG-SE and MAO-SE (R2 = 0.650). Association of SG-SE, MAO-SE and BAO or BSG (or BAO and BSG) did not increase significantly the discrimination between ZES and DU (R2 = 0.672).