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

Abstract

ObjectiveHundreds 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.Results1.76% 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.

Sensory processing and cortisol at age 4 years: Procedural pain‐related stress in children born very preterm

“…Calvi et al. (2017) found that measurement error in saliva samples due to within and between laboratory sampling was minimal.…”

Trajectories of Depressive Symptoms and Anxiety during Pregnancy and Associations with Pregnancy Stress

“…Salivary cortisol levels were measured using enzyme-linked immunosorbent assay kits supplied commercially for single measurements; the supplied standards were assayed in duplicates (R&D Systems, Minneapolis, MN, USA). The intra- and inter-assay coefficients of variation for salivary cortisol were 6.9% 1.9% and 9.9% 0.8%, respectively, which are both within recommended ranges [ 28 ].…”

Medical Diagnostic Tests: A Review of Test Anatomy, Phases, and Statistical Treatment of Data

“…However, good practice in reporting CVs is not always observed. Inter- and intra-assay CVs within laboratories reported by Calvi et al [126] on measurements of cortisol in saliva are reported as point estimators, and neither confidence intervals nor statistical test is provided. Reed et al [127] reported the variability of measurements (thirty-three laboratories with fifteen repeated measurements on each lab) of human serum antibodies against Bordetella pertussis antigens by ELISA method using just the CVs (no associated 95% confidence intervals) in relation with the expected fraction of pairs of those measurements that differ by at least a given factor ( k ).…”