A study of the chymotrypsin activity of duodenal fluid, using the method of Ravin, Bernstein, and Seligman, is presented. The method is applicable to routine assay and is a reliable reflection of pancreatic function. In addition, this assay is specific for chymotrypsin activity in contrast to the customary tests for protease activity, which use casein or gelatin as substrates. In 40 patients with complete pancreatic insufficiency due to fibrocystic disease of the pancreas the chymotrypsin activity of the duodenal fluid was not measurable (i.e., less than 5 μg. of β-naphthol liberated from the substrate).The chymotrypsin activity in 53 patients with normal pancreatic function and without symptoms referable to fibrocystic disease of the pancreas varied from 11 to 65 μg. of βd-naphthol except for the lowest value in this control group of 8 μg.In another group of 62 children with sufficient symptoms to call for duodenal fluid assay (failure to gain, abnormal feces or repeated respiratory infections) the range of chymotrypsin activity was similar to that of the control group. The duodenal fluid assay and clinical course excluded fibrocystic disease of the pancreas in this group.The chymotrypsin assay is useful in the study of patients with partial pancreatic insufficiency from progressive loss of pancreatic function as the disease progresses.In view of occasional diagnostic failures, based on assay of a single enzyme, it is important to determine the total enzyme activity of duodenal fluid for proper complete evaluation of pancreatic function.
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