Measurement of cortisol in saliva: a comparison of measurement error within and between international academic‑research laboratories

Authors

Jessica L. Calvi, University of Nebraska-LincolnFollow
Frances R. Chen, Georgia State University
Victoria Brann Benson, University of North Carolina at Chapel Hill
Eleanor Brindle, University of Washington
Matt Bristow, Anglia Ruskin University
Alpana De, Anglia Ruskin University
Sonja Entringer, University of California, Irvine
Helen Findlay, Montreal Mental Health University Institute
Christine Heim, Pennsylvania State University
Eric A. Hodges, University of North Carolina at Chapel Hill
Heiko Klawitter, Charité Universitätsmedizin
Sonia Lupien, Montreal Mental Health University Institute
Holly M. Rus, University of California, Merced
Jitske Tiemensma, University of California, Merced
Silvanna Verlezza, McGill University
Claire-Dominique Walker, McGill University
Douglas A. Granger, Johns Hopkins UniversityFollow

Date of this Version

2017

Document Type

Article

Citation

Calvi et al. BMC Res Notes (2017) 10:479 DOI 10.1186/s13104-017-2805-4.

Comments

Copyright © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License.

Abstract

Objective: Hundreds of scientific publications are produced annually that involve the measurement of cortisol in saliva. Intra- and inter-laboratory variation in salivary cortisol results has the potential to contribute to crossstudy inconsistencies in findings, and the perception that salivary cortisol results are unreliable. This study rigorously estimates sources of measurement variability in the assay of salivary cortisol within and between established international academic-based laboratories that specialize in saliva analyses. One hundred young adults (Mean age: 23.10 years; 62 females) donated 2 mL of whole saliva by passive drool. Each sample was split into multiple- 100 μL aliquots and immediately frozen. One aliquot of each of the 100 participants’ saliva was transported to academic laboratories (N = 9) in the United States, Canada, UK, and Germany and assayed for cortisol by the same commercially available immunoassay.

Results: 1.76% of the variance in salivary cortisol levels was attributable to differences between duplicate assays of the same sample within laboratories, 7.93% of the variance was associated with differences between laboratories, and 90.31% to differences between samples. In established-qualified laboratories, measurement error of salivary cortisol is minimal, and inter-laboratory differences in measurement are unlikely to have a major influence on the determined values.