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Blood biochemistry: trypsin-like immunoreactivity
(Immunoreactive trypsin, IRT, TLI) 		print.gif Feedback

Overview
  • Trypsin is a pancreatic proteolytic enzyme; if it leaks from pancreatic cells it causes pancreatitis Pancreatitis.
  • Immunoreactive trypsin (probably the trypsin precursor, trypsinogen) is present in serum/plasma and will react with anti-trypsin antibodies but has no proteolytic activity.
  • Decreased trypsin-like immunoreactivity (TLI) indicates exocrine pancreatic insufficiency Exocrine pancreatic insufficiency.
  • Increased TLI may be seen with pancreatitis.

Uses

Alone
  • Exocrine pancreatic insufficiency Exocrine pancreatic insufficiency.

In combination
  • Diagnosis of exocrine pancreatic insufficiency Exocrine pancreatic insufficiency.
  • Acute pancreatitis Pancreatitis.

Other points
  • Withdrawal of oral pancreatic enzyme supplementation is not necessary prior to testing since it does not contribute to serum levels.
  • Serum amylase and lipase are not good indicates of pancreatic disease in cats.
Sampling Top

Source of test material
  • Standard venipuncture Standard venipuncture.

Quantity of test material
  • 2 ml serum or plasma. Check with laboratory regarding minimum recommended volume for single test or in combination with other tests.

Sample collection technique
  • For sample tube preference see Blood sample tube requirements table 02.
  • Heparinized plasma or serum.
  • Immunoassays are species-specific. Assays for canine TLI do not detect feline TLI.

Quality control

Precautions
  • See biochemistry Blood biochemistry: overview for information on handling and storage.

Timing of test
  • Fast for 12 hours before sampling.
  • Equivocal TLI results may be obtained if animal has not been fasted prior to collection of serum.

Sample storage
  • Refrigerate prior to dispatch.

Sample transport
  • Package according to mailing regulations Transportation of diagnostic specimen.
Test(s) Top

Availability
  • GI Laboratory, Texas A&M University, USA.
  • SCL Bioscience Services, UK.
  • Many laboratories may have arrangements with the above specialist laboratories to perform this assay.

Validity

Sensitivity
  • Sensitive and specific for diagnosis of exocrine pancreatic insufficiency (EPI).
  • Sensitivity in pancreatitis are thought to be less than with EPI.
  • TLI may be elevated in cats with IBD. These cats may or may not have pancreatitis.

Specificity
  • Specificity in pancreatitis are thought to be less than with EPI.
Result data Top

Normal (reference) values
  • Normal reference range 12-82 microg/ml.

Abnormal values
  • Exocrine pancreatic insufficiency.
  • Elevated levels may be seen in early acute pancreatitis.
    TIP.jpg Now commonly used as a diagnostic aid for pancreatitis in the cat as it is 80% specific and 33% sensitive.

Errors and Artifacts
  • False elevations:
    • Renal failure.
    • Emaciation (possible).
  • False negatives:
    • Some cases of severe pancreatitis will not have elevated serum TLI.
  • Elevated levels may be seen in some malnourished patients without evidence of pancreatitis.
Sources Top

Publications

Refereed papers
  • Gerhardt A, Steiner J M, Williams D A, Kramer S, Fuchs C, Janthur M, Hewicker-Trautwein M, Nolte I (2001) Comparison of the sensitivity of different diagnostic tests for pancreatitis in cats. J Vet Intern Med 15 (4), 329-333.
  • Simpson K W, Fyfe J, Cornetta A, Sachs A, Strauss-Ayali D, Lamb S V, Reimers T J (2001) Subnormal concentrations of serum cobalamin (vitamin B12) in cats with gastrointestinal disease. 15 (1), 26-32.
  • Simpson K W (2000) The emergence of feline pancreatitis. J Vet Intern Med 15 (4), 327-328.
  • Swift N C, Marks S L, MacLachlan N J, Norris C R (2000) Evaluation of serum feline trypsin-like immunoreactivity for the diagnosis of pancreatitis in cats. JAVMA 217 (1), 37-42.
  • Bruner J M, Steiner J M, Williams D A, Van Alstine W G, Blevins W (1997) High feline trypsin-like immunoreactivity in a cat with pancreatitis and hepatic lipidosis. JAVMA 210 (12), 1757-1760.
  • Horney B (1996) Clinical pathology interpretation. Can Vet J 37 (4), 244-245.

Other sources of information
  • Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine. 5th edn. Philadelphia: W B Saunders & Co. ISBN: 0 7216 6795 3.
  • Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press. ISBN: 0 1239 6305 2.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.

Vetstream contributor(s)
  • Dr Kathleen P Freeman DVM MS PhD MRCVS, Idexx Laboratories, PO Box 4, Wetherby, West Yorkshire LS22 4ZR, UK.
  • Dr Kenneth Simpson BVM&S PhD, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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Blood biochemistry: overview
Blood sample tube requirements table 02
Exocrine pancreatic insufficiency
Pancreatitis
Standard venipuncture
Transportation of diagnostic specimen
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