Update on the evaluation of pancreatic exocrine status in cystic fibrosis

Purpose of review: Pancreatic functional status has a very strong effect on outcome in cystic fibrosis and pancreatic insufficiency requires lifelong treatment with pancreatic enzymes. Traditionally, clinical signs and symptoms have been used to decide who should be treated with pancreatic enzyme supplements; however, recent studies show that patients with cystic fibrosis are both undertreated and overtreated using this approach. This paper reviews recent progress in the development of noninvasive, indirect tests of pancreatic function for use as diagnostic tools for patients with cystic fibrosis. Recent findings: Breath testing using ¹³C-labeled fat and measurement of several pancreatic enzymes in stool, such as chymotrypsin, lipase, and elastase have been explored as ways to define pancreatic functional status. Fecal elastase has good sensitivity, specificity, and positive and negative predictive value for defining severe pancreatic insufficiency in patients with cystic fibrosis and appears to be more useful than measurement of other fecal enzymes. Its role in milder pancreatic insufficiency and in disease states other than cystic fibrosis, such as chronic pancreatitis, is less clear. Summary: Several new noninvasive, indirect tests of pancreatic function have been developed to aid in the definition of pancreatic functional status in patients with cystic fibrosis. An objective measure of pancreatic functional status should be obtained in all patients with cystic fibrosis, and the recent development of new screening tools such as fecal elastase makes this feasible.