A rapid, endoscopic exocrine pancreatic function test and the Lundh test: a comparative study

Background/aims: The diagnosis of chronic pancreatitis is often difficult in the early stages of the disease. Morphological tests may be normal, and reliable methods for the evaluation of the exocrine pancreatic function are time-consuming and troublesome. A new test for exocrine pancreatic function, using endoscopic aspiration of secretin-stimulated pancreatic juice, has been developed. We evaluated the test using the Lundh meal test as reference.

Methods: The endoscopic secretin stimulation test (ESST) was performed in a consecutive row of 24 patients referred for pancreatic function testing because of clinical suspicion of chronic pancreatitis and in 23 healthy volunteers. The participants fasted overnight and secretin was given intravenously (1 CU/kg) as a bolus the following morning. Thirty minutes after administration of secretin, the tip of the duodenoscope was placed close to the ampulla of Vater and duodenal aspirate was drawn for 10 min. Intraduodenal concentrations of lipase, bicarbonate, elastase and zinc were measured. The concentration of lipase during the Lundh test (4 x 20 min aspiration) was used as reference test in the patients.

Results: Judged from the Lundh test, the exocrine pancreatic function was nearly abolished in 5 patients (<10% of lower normal limit), reduced in 6 patients and normal in 13 patients. ESST failed in 1 patient (no aspirate). Lipase concentrations (KU/l) were significantly lower in the patients with nearly abolished function compared to patients with reduced or normal exocrine pancreatic function (NEPF; Mann-Whitney U test: p < 0.01), but an overlap was found between patients with reduced exocrine pancreatic function [100.1 (median); 60.0-225.0 (range)] patients with NEPF (145.7; 44.6-268.0) and healthy controls (175.0; 84.8-381.0). Bicarbonate concentrations (mEq/l) were significantly lower in patients with reduced exocrine pancreatic function (51.2; 32.5-69.6) compared to patients with NEPF (80.0; 48.1-101.8; Mann-Whitney U test: p < 0.05). Pancreatic elastase concentration was significantly lower in the group with nearly abolished exocrine function compared to patients with NEPF (Mann-Whitney U test: p < 0.05), but there was no difference between elastase concentrations among the other groups. We found significant correlation between lipase and bicarbonate concentrations during ESST and lipase concentrations during the Lundh test in all 23 patients (Spearman's Rank test: rho = 0.597 and 0.683, respectively, p < 0.01). By using receiver operating characteristic curves, best cut-off point for bicarbonate was estimated. Lipase and bicarbonate results in the healthy volunteers were not statistically different from results in patients with NEPF. No side effects were observed except for worsening of nausea and abdominal pain in 2 of the patients.

Conclusion: The ESST is safe, and by combining the estimation of lipase and bicarbonate concentrations this test is a rapid, easy and useful diagnostic test for exocrine pancreatic function.