[Amino acid level in plasma--expressed as alpha-amino-nitrogen--reaction to stimulation of the exocrine pancreas: approaches to a new pancreatic function test].

We determined by the ninhydrin method the plasma amino acid (AA) levels prior to, during and following, a 1-hour i.v. infusion of 1 U/kg body weight each of secretin and pancreozymin in patients with normal (n = 74) or reduced (n = 39) exocrine pancreatic function, as assessed by the duodenal aspiration test. The results of the two tests correlated significantly with each other (p less than 0.001). A maximum AA decrease of greater than or equal to 12% was observed in all patients with a normally functioning pancreas (specificity 100%), and of less than 12% in all patients with medium to high-grade impairment of pancreatic function (sensitivity 100%). Since, however, low-grade pancreas insufficiency (20-40% of the mean normal enzyme output) is recognized in fewer than one-half of the cases, the overall sensitivity of the AA-consumption test decreases to 69%. The results can, however, be improved by: 1) Calculating the mean percentage AA decrease with a limit value of 5% (sensitivity 90%); 2) determining individual AA with pancreas-specific absorption, such as serine (sensitivity 92%); 3) dropping the lower normal value of exocrine pancreatic function to 25% of the normal mean enzyme output (sensitivity 96%). Diseases that may be associated with the most common condition that causes pancreatic insufficiency--chronic pancreatitis--and which have an influence on AA metabolism, such as cirrhosis of the liver and diabetes mellitus, have no influence on the accuracy of the AA consumption test, which, considered overall, represents a competitive alternative to other tubeless tests of pancreatic function.