Peer-reviewed veterinary case report
Comparing blood cortisol tests in dogs using radioimmunoassay
By Russell, N J et al.·Published in Australian veterinary journal·2007·School of Veterinary & Biomedical Sciences, Australia·View original on PubMed →
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Original publication title: Comparison of radioimmunoassay and chemiluminescent assay methods to estimate canine blood cortisol concentrations.
- Species:
- dog
Plain-English summary
A group of 54 dogs had their blood cortisol levels tested to compare two different lab methods: a traditional radioimmunoassay and a newer chemiluminescent assay. The results showed that while both methods generally agreed, there were significant differences in cortisol levels for some lower concentrations, which could affect treatment decisions. This means that if your dog has low cortisol levels, it's important to ensure the lab's method is reliable. Overall, both tests can be useful, but caution is advised when interpreting lower results from the chemiluminescent assay.
People also search for: dog cortisol test results · low cortisol levels in dogs · adrenal function testing in dogs
Abstract
BACKGROUND: 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. OBJECTIVES: 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. METHODS: 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). RESULTS: Overall, there was a strong correlation (r2=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 (r2=0.869, P<0.001), <100 nmol/L (r2=0.790, P<0.001), and <40 nmol/L (r2=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. CONCLUSIONS: 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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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/18042154/