Development and validation of a radioimmunoassay for the measurement of canine pancreatic lipase immunoreactivity in serum of dogs

Objective - To develop and validate a radioimmunoassay (RIA) for measuring canine pancreatic lipase immunoreactivity (cPLI) in serum obtained from dogs. Sample Population - Serum samples from 47 healthy dogs. Procedures - Canine pancreatic lipase (cPL) was purified from pancreatic specimens of dogs. Antibodies against cPL were raised in rabbits and purified by use of affinity chromatography. A tracer was produced by iodination of cPL with ¹²⁵I. An RIA was established and validated by determination of sensitivity, working range, dilutional parallelism, spiking recovery, and intra- and interassay variability. A reference range for cPLI in serum was established by use of the central 95th percentile for samples obtained from 47 healthy dogs. Results - Sensitivity and upper limit of the working range were 0.88 and 863 μg/L, respectively. Observed-to-expected ratios for serial dilutions ranged from 84.9 to 116.5% for 4 samples. Observed-to-expected ratios for spiking recovery ranged from 82.8 to 128.6% for 4 samples. Coefficients of variation for intra-assay variability for 4 serum samples were 18.3, 4.2, 3.5, and 8.9%, whereas interassay coefficients of variation were 29.2, 6.2, 3.9, and 4.4%, respectively. The reference range was 4.4 to 276.1 μg/L. Conclusions and Clinical Relevance - We conclude that the RIA described is sensitive, linear, accurate, precise, and reproducible, with limited accuracy in the high end of the working range and limited precision and reproducibility in the low end of the working range. Additional studies are needed to evaluate whether this degree of accuracy, precision, and reproducibilty will negatively impact clinical use of this assay.