THE DIAGNOSIS of cystic fibrosis is classically based on a clinical picture of recurrent respiratory involvement in the form of cough, wheezing, and respiratory distress, and gastrointestinal signs of frequent, bulky, foul stools and hyperphagia. Confirmation of the diagnosis has depended on the demonstration of the elevation of sweat-sodium chloride and deficiency of pancreatic enzymes. In the past decade the ease and reliability of the sweat test has led to its use and substitution for the duodenal intubation for pancreatic enzymes. While some have completely stopped the appraisal of pancreatic insufficiency, others have utilized indirect techniques for assessment of digestive defect, eg, lipoidol excretion, stool trypsin by film test, radioactive fat absorption and excretion, and various absorption tests.
With increasing experience in the differential diagnosis of cystic fibrosis, it has become apparent that there are a number of instances where the sweat test for sodium or chloride falls within the