Studies on cystic fibrosis of the pancreas; role of various diluents and the dilution factor in the interpretation of the x-ray film test for fecal trypsin.

Abstract

FALSELY positive tests for fecal trypsin due to bacterial gelatinase 1 were found for more than one-half of 137 children²with cystic fibrosis of the pancreas whose feces were tested by the x-ray-film technique.³Previous studies⁴have indicated that soybean trypsin inhibitor will inhibit gelatin liquefaction due to pancreatic trypsin and pancreatin-U.S.P. but not that due to bacterial gelatinase. The reliability and consistency of results obtained by the "spot film" technique for fecal trypsin are affected by the following factors: (1) The pH of the fecal suspension¹(2) Age of the specimen (3) Consistency of the stool (4) Differences in the type of x-ray and photographic film used in the test⁵(5) Presence of barium and certain other heavy metal ions in high concentration in the fecal specimen⁶(6) Temperature at which the fecal suspension is incubated on the x-ray film (7) Presence of bacterial gelatinase⁷