The TLI test is highly sensitive and specific for the diagnosis of canine exocrine pancreatic insufficiency (EPI) (link to : disease/epi) . This test measures the concentration of trypsin-like proteins in a blood sample by radioimmunoassay. These proteins diffuse into the blood stream in small amounts (0.01-0.1% of pancreatic trypsinogen).

In normal dogs the TLI concentrations are greater than 5.5m g /L (up to 35m g/L)

In dogs with exocrine pancreatic insufficiency TLI concentrations are less than 2.5 m g/L.

In dogs with pancreatitis TLI can be normal or increased.

Dogs with bacterial overgrowth have a normal TLI test - unless exocrine pancreatic insufficiency is present as well

False negative results may occur if a dog has concurrent pancreatitis (increasing TLI) and exocrine insufficiency.