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Salivary cortisol measurement in horses: immunoassay or LC-MS/MS?
Journal article

Salivary cortisol measurement in horses: immunoassay or LC-MS/MS?

  • Sauer FJ Swiss Institute of Equine Medicine (ISME), Vetsuisse Faculty, Department of Clinical Veterinary Medicine, University of Bern, and Agroscope, Switzerland, Laenggassstrasse 124, 3012 Bern, Switzerland. Electronic address: fay.sauer@web.de.
  • Gerber V Swiss Institute of Equine Medicine (ISME), Vetsuisse Faculty, Department of Clinical Veterinary Medicine, University of Bern, and Agroscope, Switzerland, Laenggassstrasse 124, 3012 Bern, Switzerland.
  • Frei S Department of Nephrology and Hypertension and Department of BioMedical Research, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse 15, 3010 Bern, Switzerland.
  • Bruckmaier RM Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bremgartenstrasse 109a, 3012 Bern, Switzerland.
  • Groessl M Department of Nephrology and Hypertension and Department of BioMedical Research, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse 15, 3010 Bern, Switzerland.
  • 2020-04-06
Published in:
  • Domestic animal endocrinology. - 2020
ACTH stimulation test
Horse
Immunoassay
Liquid chromatography-tandem-mass spectrometry
Salivary cortisol
English The aim of the present study was to measure salivary cortisol concentrations of horses before and after hypothalamic-pituitary-adrenal (HPA) axis stimulation by means of liquid chromatography-tandem-mass spectrometry (LC-MS/MS) and an immunoassay (cELISA) for method comparison. Nine clinically healthy horses participated in the study. An ACTH stimulation test was performed. Saliva samples were collected before (T0) and 60 (T60) min after intravenous injection of 1 μg/kg BW synthetic ACTH1-24. LC-MS/MS was assessed for the determination of equine salivary cortisol. The results of these measurements were then compared to the results obtained by a cELISA, which has previously been validated for use in horses. The Pearson correlation coefficient was calculated and showed no correlation at T0 (r = -0.2452; P = 0.5249) and significantly correlated results at T60 (r = 0.8334; P = 0.0053). Bland-Altman-Plots of T60 revealed that immunoassay measurements led to higher outcome values than LC-MS/MS. On average, immunoassay results were 2.3 times higher. Poor agreement between both methods at T0 is potentially a consequence of inaccuracy in the very low measuring range of the immunoassay, and to a smaller extent, structurally similar cross-reacting agents and matrix effects, which might bias the results. Overestimation of immunoassay results at T60 might be due to different standardization of both methods, non-avoidable matrix effects on the antigen-antibody interaction in the ELISA, and possibly cross-reactions of other steroids. While immunoassay measurements of equine salivary cortisol yielded higher but reasonably correlated results for elevated cortisol concentrations after stimulation of the HPA axis, LC-MS/MS provided more accurate results, particularly for baseline cortisol concentrations close to the limit of detection of the ELISA.
Language
  • English
Open access status
closed
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Persistent URL
https://sonar.ch/global/documents/46848
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