Trypsin Like Immunoreactivity

Indications for performing this test: Any case of chronic diarrhea and weight loss should include a TLI test to rule out exocrine pancreatic insufficiency. If the TLI is negative and there is no further evidence of pancreatic disease, the diagnostic focus can be shifted to assessment of small intestine function .

TLI is most often used in the detection of exocrine pancreatic insufficiency (EPI). The TLI may also be used to detect pancreatic necrosis, although it's increase in these cases is inconsistent. Because of its short half-life, only 6 hours, TLI activity will increase before the serum activity of either lipase or amylase. This test is species specific and measures the levels of trypsinogen in the blood. In normal animals, small amounts of this enzyme diffuse into the circulation. Because the serum level depends on pancreatic mass, atrophy of the pancreas associated with EPI will lead to reduced serum levels.

Exocrine Pancreatic Insufficiency: Notice how the pancreas is shrunken and no longer producing adequate enzymes.

Special consideration in cats: Feline pancreatitis is a very difficult diagnosis to make. Serum amylase and lipase levels have shown to be unreliable indicators of pancreatic disease in cats. Studies on the reliability of TLI have provided conflicting results. While some believe that TLI may be a more sensitive indicator of feline pancreatitis, others have shown that TLI is elevated only sporadically and therefore does not provide reliable evidence of pancreatitis. The lack of any definitive diagnostic aid is testimony to the difficulty of this diagnosis and provides insight into the low frequency of reported cases of pancreatitis in cats. Most cases most likely go unrecognized in a clinical setting. See feline PLI (pancreatic lipase) for a more promising test to diagnose feline pancreatitis.

On the other hand, it has been recently shown that TLI is a reliable test for feline Exocrine Pancreatic Insufficiency. This is mainly due to the use of feline or canine specific TLI tests.

Trypsin-like Immunoreactivity (TLI)