Comparison of four provocative tests for the diagnosis of gastrinoma

In an attempt to determine the best provocative test for the diagnosis of gastrinoma, ten normal subjects, 13 patients with known gastrinoma, and one patient with presumed gastrinoma were administered four regimens: (1) rapid calcium infusion (2 mg Ca++/kg/min), (2) secretin (2 clinical units (CU)/kg/bolus), (3) long calcium infusion (12 mg Ca++/kg/3 h) and (4) a combination test consisting of a rapid calcium infusion followed immediately by secretin. Blood was drawn for serum gastrin levels before and following infusion of the test agents. The administration of rapid calcium followed by secretin provoked the greatest increases in serum gastrin above basal levels in both normals (29%) and patients (362%). Peak gastrin levels in patients were similar following the long calcium infusion (341%) but were less following the rapid calcium infusion alone (124%) and secretin alone (207%). There were no false-positive or false-negative tests with the calcium plus secretin when the criterion for diagnosis was either a 50% increase or a 200 pg/ml increase above the basal gastrin level. The distinct advantages (short test period, low patient morbidity, and relatively great potency) of the calcium plus secretin test make it an attractive alternative to other previously described provocative tests for the diagnosis of gastrinoma.