Lack of accuracy of plasma alpha-amino nitrogen profiles as an indicator of exocrine pancreatic function both after continuous and bolus stimulation of the pancreas with secretin and cholecystokinin-pancreozymin

Abstract

Background: The reduced decrease of plasma alpha-amino nitrogen after hormonal stimulation of the pancreas has been characterized as a valid and simple test of pancreatic function. Aim of this study was to reassess the clinical value of the alpha-amino nitrogen test and to evaluate the role of different modes of hormonal secretion. Therefore, we have investigated the relationship of plasma alpha-amino nitrogen responses and pancreatic secretion, stimulated by either bolus injection (n = 25) or continuous infusion (n = 32) of cholecystokinin-pancreozymin in patients with and without exocrine pancreatic insufficiency as determined by the secretin-pancreozymin test. Of the 57 patients referred to the secretin-pancreozymin-test, 18 had pancreatic insufficiency, each 9 in the group with continuous and bolus stimulation.

Results: Basal alpha-amino nitrogen concentrations were almost identical in patients with and without impaired pancreatic function (2.66 +/- 0.12 mmol/l vs. 2.73 +/- 0.08 mmol/l [SEM]; p > 0.05). Both, the bolus dose and infusion of cholecystokinin induced similar (log-normally distributed) maximum decreases of alpha-amino nitrogen concentrations (-SD; mean; + SD: 3.6; 9.0; 22.3% vs. 6.0; 10.5; 18.5%, respectively) in the patients without exocrine pancreatic insufficiency. This was in tendency more pronounced compared to those with impaired pancreatic secretion (cholecystokinin bolus; 2.7; 5.2; 9.9%; infusion: 5.0; 7.7; 11.6%). The difference (+/- exocrine pancreatic insufficiency) was significant (p < 0.05) for the infusion mode only. Moreover, the time course of alpha-amino nitrogen concentration-profiles was more homogenous after hormone infusion as compared to bolus stimulation. Sensitivities to detect exocrine pancreatic insufficiency by the alpha-amino nitrogen test were < 50% with either test modification.

Conclusion: The decrease of plasma alpha-amino nitrogen after stimulation with cholecystokinin is no accurate indicator of exocrine pancreatic function, regardless of whether hormonal stimulation is by bolus or by infusion.