Serum trypsinlike immunoreactivity measurement for the diagnosis of subclinical exocrine pancreatic insufficiency.

Dogs (n = 158) with serum trypsinlike immunoreactivity (TLI) concentrations < or = 5.0 microg/L were studied. The diagnosis of clinical exocrine pancreatic insufficiency (EPI) was made in 114 of 158 dogs based on TLI concentration < 2.5 microg/L and clinical signs typical of EPI (eg, polyphagia, voluminous feces, weight loss). In 44 of 158 dogs, a single TLI measurement and clinical signs were not diagnostic. In 9 of 44 dogs, TLI was < 2.5 microg/L, indicating EPI, but the gastrointestinal signs were atypical or the dogs were asymptomatic. In 35 of 44 dogs, TLI was 2.5-5.0 microg/L. All 44 dogs were retested for TLI within 1-27 months (mean, 11.9 months). In 20 of 44 dogs, the retested TLI was normal (> 5.0 microg/L). In 4 of 44 dogs with clinically diagnosed EPI, the retested TLI was < 2.5 microg/L. In the remaining 20 of 44 dogs, TLI was persistently < 5.0 microg/L (range, 1.0-4.9 microg/L; mean, 3.1 microg/L). Of these dogs, 15 had no clinical signs of gastrointestinal disease, and 5 had occasional clinical signs atypical for EPI. Gross examination of the pancreas (12 dogs) showed that the amount of normal pancreatic tissue was remarkably diminished. These dogs were diagnosed with subclinical EPI. The TLI-stimulation test, in which TLI is measured before and after stimulation with secretin and cholecystokinin, showed a significant response (P < .05) both in dogs with subclinical EPI and in control dogs, but showed no response in dogs with clinical EPI. In this study, EPI was diagnosed in its subclinical phase by TLI concentrations persistently < 5.0 microg/L, and a single TLI concentration < 5.0 microg/L was not diagnostic. Retesting after TLI concentrations < 5.0 microg/L is recommended even in clinically normal dogs, because of the possibility of subclinical EPI.