Inter-method comparison of salivary cortisol measurement

Abstract

Background: Salivary cortisol is increasingly used in the diagnostic work-up of suspected Cushing's disease as well as in stress research. In this study, the agreement of different methods for salivary cortisol measurement was assessed. Methods: Saliva samples from five healthy volunteers were distributed to three routine clinical chemistry laboratories. As a reference, all samples were also analyzed using liquid chromatography-tandem mass spectrometry involving stable isotope labeled cortisol for internal standardization in our laboratory. Results: All immunometric routine methods substantially overestimated salivary cortisol concentrations by approximately 50%. The agreement between these immunoassays was moderate with between-method coefficients of variation of up to 36% for individual samples. Conclusions: Standardization of salivary cortisol measurement requires substantial improvement, in particular by implementation of proficiency testing schemes, a defined reference method, and reference materials. Interpretation of salivary cortisol data in psycho-neuroendocrinological research has to consider the inappropriate level of standardization realized for salivary cortisol measurement to date.

A comparison of salivary testosterone measurement using immunoassays and tandem mass spectrometry

“…Testosterone EIAs are found to cross-react with other steroids (Chattoraj, 1976) and biological agents (e.g., sex hormone-binding globulin; Pugeat et al, 1981). Consistent with this research Running head: TESTOSTERONE MEASUREMENT IMMUNOASSAYS 4 on testosterone measurement, previous studies of cortisol have revealed differences in predicted salivary cortisol concentrations across assay kits (e.g., Baecher et al, 2013;Miller et al, 2013). These differences have been attributed to differing specifications of kits and cross-reactivity in EIAs.…”

“…Although many companies manufacture assay kits for commercial use, recent work suggests that these different kits vary in concentration predictions for the same hormones (e.g., Taieb et al, 2003;Baecher et al, 2013;Crewther et al, 2013). Some potential reasons for differences in the estimation of hormone levels across kits include differing levels of sensitivity and specificity across the range of hormonal concentrations, with the lowest and highest concentrations being most prone to quantification errors .…”

Saliva cortisol in relation to aircraft noise exposure: pooled-analysis results from seven European countries

“…It also allows for potential measurement differences between HYENA and DEBATS related to sampling and laboratory analysis: the ELISA (enzyme-linked immunosorbent) method in the DEBATS study and the RIA (radioimmunoassay) method in the HYENA. For morning and evening cortisol levels, the use of the linear relationship between ELISA and RIA methods [35] makes levels of cortisol concentrations directly comparable for the HYDE study. Regression conclusions were similar to those presented in Table 3, carried out without the use of this equation.…”

“…Compared to controls, RIA gave results much closer to the expected value than ELISA did [33]. Although measurements concerned only 10 samples, Baecher et al (2013) published Passing and Bablock regression of salivary cortisol results reported by immunoassay systems related to a reference (35). Regression equations showed a strong linear relationship between ELISA and RIA methods: RIA = 0.92 (95% CI: 0.87–1.03) × ELISA-0.19 (95% CI: − 0.35 to − 0.04); r = 0.993.…”