Development and validation of a radioimmunoassay for feline trypsin-like immunoreactivity.

OBJECTIVE: To develop and validate a radioimmunoassay for feline trypsin-like immunoreactivity (fTLI). PROCEDURE: A double antibody radioimmunoassay for determination of fTLI was developed, using feline trypsin purified from feline pancreatic tissue antiserum against feline trypsin raised in New Zealand White rabbits, and a commercially available precipitation solution. This assay was validated by determining detection limit, linearity, accuracy, and intra- and interassay variabilities. A control range was determined from samples of 21 clinically normal cats. RESULTS: The detection limit for fTLI in this assay was 1.9 micrograms/L. The linearity of the assay was evaluated by testing dilutional parallelism. Observed/expected values ranged between 95 and 127%. The accuracy of the assay was tested by measuring recovery of added trypsin. Observed/expected values ranged from 99 to 114%. Intra-assay variability ranged between 3.0 and 9.4%, and interassay variability ranged between 4.0 and 8.2%. The control range for serum fTLI was determined to be 17.1 to 48.6 micrograms/L. CONCLUSION: The assay for fTLI described here is sensitive, linear, accurate, precise, and reproducible. CLINICAL RELEVANCE: This assay may be of use for the diagnosis of exocrine pancreatic diseases in cats. Preliminary results of such research have been promising, and further clinical studies are in progress.

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