Is the fluorescein dilaurate test suitable for monitoring the effectiveness of pancreatic enzyme replacement therapy?

We have employed an oral test of pancreatic digestive function using fluorescein dilaurate (a substrate for pancreatic cholesterol ester hydrolase), administered together with pancreatic enzyme supplements, in order to test the hypothesis that urinary excretion of fluorescein provides a simple method for determining the optimal dose of oral pancreatic enzymes. Commercially available pancreatic enzyme supplements had negligible cholesterol hydrolase activity in vitro, and did not increase the urinary excretion of fluorescein when administered together with fluorescein dilaurate in 16 patients with pancreatic exocrine insufficiency. Inhibition of gastric secretion by ranitidine resulted in a statistically significant increase in urinary fluorescein excretion during the fluorescein dilaurate test. The fluorescein dilaurate test is not, therefore, suitable for determining the effectiveness of oral pancreatic enzyme replacement therapy. Moreover, the manufacturer's advice to stop oral pancreatic enzyme therapy for 5 days before performing the fluorescein dilaurate test appears unnecessary, since oral pancreatic enzymes do not alter test results.