Serum trypsinlike immunoreactivity in cystic fibrosis. An aid in assessing progressive involvement of the pancreas.

Serum trypsinlike immunoreactivity (TLI) was measured in 42 children with cystic fibrosis (CF) and related to age and steatorrhea. The mean TLI value in 106 age- and sex-matched control subjects was 22 +/- 7.2 ng/mL. In patients with CF, TLI showed a widespread distribution (range, 0.3 to 214 ng/mL), and an exponential inverse correlation between TLI and age was found. The same trend in the decline in TLI values with increasing age was evident in patients who were followed up. Reduced TLI concentrations were associated with fat malabsorption, but in younger patients with CF, normal or elevated TLI values did not exclude steatorrhea. Elevated serum TLI levels in patients with CF at an early age might reflect pancreatic ductal obstruction. Tendency for TLI to decrease with advancing age and in patients who are followed up can reflect ongoing degenerative destruction within the pancreatic gland. Serum TLI estimation in patients with CF should be used to monitor the progression of pancreatic impairment.