Fecal chymotrypsin: a new diagnostic test for exocrine pancreatic insufficiency in children with cystic fibrosis.

The purpose of this report is to evaluate whether a new, simple, non-invasive method for chymotrypsin measurement in stools is useful for the diagnosis of exocrine pancreatic insufficiency in cystic fibrosis (CF). A hundred children aged from 2 months to 12 years were tested: 50 children had been admitted for chronic diarrhoea, 15 for cystic fibrosis and 40 acted as controls. Chymotrypsin in stools was assayed using a kinetic measurement with Succ-Ala-Ala-Pro-Phe-pNa as substrate in a simple photometric assay. In 13 of 15 children with cystic fibrosis, stool enzyme levels were always remarkably low, while all control subjects and all children not presenting cystic fibrosis had normal stool levels of chymotrypsin. Our data suggest that stool chymotrypsin measurement is a simple and reliable "tubeless" test for the evaluation of exocrine pancreatic insufficiency in children with cystic fibrosis.