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Comparison of radioimmunoassay and chemiluminescent assay methods to estimate canine blood cortisol concentrations
Journal article   Peer reviewed

Comparison of radioimmunoassay and chemiluminescent assay methods to estimate canine blood cortisol concentrations

N.J. Russell, S.F. Foster, P. Clark, I.D. Robertson, D. Lewis and P.J. Irwin
Australian Veterinary Journal, Vol.85(12), pp.487-494
12/2007
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Abstract

Non-radioactive assay methods are widely used in commercial laboratories to measure canine blood cortisol concentrations, despite a paucity of published validity data of these tests compared with the traditional 'gold standard' radioimmunoassay. To compare a commercial chemiluminescence assay with radioimmunoassay for blood cortisol measurement, determine the effect of storage on the radioimmunoassay, and determine the impact of any differences on clinical decisions. The study included 54 client owned dogs undergoing adrenal function testing. Fresh plasma or serum samples (n = 170) were assayed for cortisol using radioimmunoassay (RIA1). Samples (n = 196) were also frozen and stored in batches, and assayed by chemiluminescence and radioimmunoassay (RIA2). Overall, there was a strong correlation (r 2 = 0.967, P < 0.001) between RIA2 and chemiluminescence concentrations without significant difference between means. Strong correlations were present for RIA2 and chemiluminescence at concentration subgroups of > 400 nmol/L (r 2 = 0.869, P < 0.001), < 100 nmol/L (r 2 = 0.790, P < 0.001), and < 40 nmol/L (r 2 = 0.738, P < 0.001). Significant differences between means were present for RIA2 and chemiluminescence concentrations in the < 100 nmol/L, and < 40 nmol/L (P < 0.001) groups. Despite a significant difference in RIA1 and RIA2 results overall, there was no significant difference between RIA1 and RIA2 for any of the concentration groups. In seven cases, discrepant RIA2 and chemiluminescence results may have altered clinical decisions. Although RIA and chemiluminescence cortisol concentrations appear highly correlated, a significant difference may exist for concentrations less than 100 nmol/L in stored canine sera. Results of chemiluminescence cortisol assays should be interpreted with caution unless the specific assay method in the laboratory has been adequately validated in dogs.

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Collaboration types
Domestic collaboration
Citation topics
3 Agriculture, Environment & Ecology
3.232 Veterinary Sciences
3.232.1281 Veterinary Reproductive Health
Web Of Science research areas
Veterinary Sciences
ESI research areas
Plant & Animal Science
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