The aim of this study was to evaluate the controversial specificity of the plasma amino acid (AA)-consumption test in detecting pancreatic diseases by using two different quantitative methods. A total of 55 subjects: 13 healthy subjects, 13 patients with chronic pancreatitis (three mild/moderate, eight severe), 13 patients with pancreatectomy and complete suppression of the exocrine pancreatic secretion, eight patients with chronic liver disease (five with impaired synthetic function), and eight patients with chronic renal failure. Total plasma AAs were quantified by a colorimetric method (p-benzoquinone) in all subjects, at 0, 30, 45, and 60 min during and 30 min after minute 60 of i.v. cerulein infusion (50 ng/kg/h). Either total and individual AAs were quantified by chromatography (high-performance liquid chromatography; HPLC) in 10 healthy subjects, 10 patients with pancreatectomy, and 10 with chronic pancreatitis at 0 and 60 min after the start of the cerulein infusion. For the colorimetric method, healthy subjects had maximal percentage decreases of total AA concentrations not significantly different from those of patients with pancreatectomy and significantly higher than those of patients with chronic pancreatitis (p < 0.0001) or chronic liver disease (p < 0.001). Pancreatic function, as assessed by fecal elastase-1 test, was not significantly correlated to the maximal percentage decrease in total plasma AAs. For the chromatographic method, total AA concentrations were not significantly correlated to those determined by colorimetry. The concentration of each of the individual plasma AAs varied considerably in each group. Fecal elastase-1 values were normal (> or = 200 microg/g) in all patients without pancreatic disease and in only one of 11 patients with chronic pancreatitis and exocrine insufficiency. The type of method used can explain the different results of the AA-consumption test. This test is not very specific for the pancreas.