PERFORMANCE EVALUATION OF THE IN-CLINIC IMMUNOASSAY SPEED CORTISOL FOR THE MEASUREMENT OF CIRCULATING CORTISOL IN DOGS
Introduction
Blood cortisol concentrations are used as an indicative marker for the pituitary and adrenal function. The objective of this study was the validation of the in-clinic immunoassay Speed CortisolTM, for the measurement of the blood irculating cortisol in dogs, employed for the support of diagnosis and treatment follow-up, in pituitary-adrenal related diseases.
Materials and Method
Samples: Cortisol was measured in 340 canine clinical blood samples before and after an ACTH stimulation test or Low Dose Dexamethasone Suppression Test (LDDST).
Methods: Cortisol levels were measured with a chemiluminescent-enzyme immunoassay (IMMULITE® 2000, Siemens) at the clinical pathology laboratory, VetAgro Sup and subsequently the samples were transferred to BVT-Virbac and assayed with the in-clinic quantitative immunoassay Speed CortisolTM (BVT- Virbac, France).
Results
Analysis: Bias calculation using the Bland-Altman method leads to a negative bias (mean +16 ; 95% CI : +11 to +22 nmol/L). Deming’s regression analysis of the data set indicates a slope coefficient of 0.98 (95% CI 0.94 to 1) and Y- intercept of -14 (95% CI -7,5 to -21). The correlation coefficient R2 was 0,92 indicating an excellent correlation in a wide range of values, between Speed CortisolTM and IMMULITE® 2000, considered to be the reference method in this study.
Conclusion
The Speed CortisolTM immunochromatographic test, has an excellent correlation with the chemiluminescent-enzyme immunoassay and it can be counted as a reliable tool for in-clinic cortisol measurement.