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

• Published in: BMC research notes Vol. 10; no. 1; p. 479
• Main Authors: Calvi, Jessica L, Chen, Frances R, Benson, Victoria Brann, Brindle, Eleanor, Bristow, Matt, De, Alpana, Entringer, Sonja, Findlay, Helen, Heim, Christine, Hodges, Eric A, Klawitter, Heiko, Lupien, Sonia, Rus, Holly M, Tiemensma, Jitske, Verlezza, Silvanna, Walker, Claire-Dominique, Granger, Douglas A
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 13.09.2017; BioMed Central; BMC
• Subjects: Adult; Biochemical assays; Clinical Chemistry Tests - standards; Cortisol; Expected values; Female; Hormones; Humans; Hydrocortisone; Hydrocortisone - analysis; Immunoassay; Immunoenzyme Techniques - standards; Inter-assay; Inter-laboratory variation; Intra-assay; Laboratories; Male; Measurement; Methods; Physiological aspects; Reproducibility of Results; Research Note; Saliva; Saliva - chemistry; Salivary cortisol; Software; Studies; Young Adult; United States; Germany; Inter-assay; Inter-laboratory variation; Intra-assay; Salivary cortisol
• ISSN: 1756-0500; 1756-0500
• DOI: 10.1186/s13104-017-2805-4

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 cross-study 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. 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.