Saliva collection method affects predictability of serum cortisol
Introduction
Cortisol is an important adrenal biomarker which can be measured in serum, urine or saliva. In addition to the assessment of adrenocorticotropic function and therapeutic monitoring it is an important analyte in stress research. In clinical routine, total serum cortisol (TSC) is the standard measurement when evaluating basal or diurnal cortisol levels.
Because it represents the amount of free and thus biologically active cortisol [1], [2], salivary cortisol measurement has become increasingly important. Additionally this technique is a non-invasive method that is not painful like drawing blood and, therefore, does not provide an additional stressor. The most common methods for saliva collection are via cotton swab (Salivette®, Sarstedt, Nümbrecht, Germany) and via passive drooling into a plastic tube.
Several studies indicate that the sampling method has an impact on the amount of measured cortisol in saliva [3], [4], [5], [6], [7]. All the same no parallel comparison of these salivary cortisol measurements with total serum cortisol and calculated free serum cortisol (FSC) values has been performed. Before this background it was our aim to compare both saliva collection methods concerning the amount of measured cortisol and to set them into relation to FSC and TSC as reference values.
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Study participants and design
Ten healthy volunteers (5 males, 5 females, mean age 31.7 years, range 22–46 years) participated in the study. None of the volunteers received oral medication (e.g. glucocorticoids, thyreoid hormones, and insulin) sensitizing the adrenocorticotropic function or had a history of taking these medications. Furthermore, none of the participants had an acute concurrent inflammation/infection (e.g. oral or pharyngeal) as determined by measurement of C-reactive Protein (CrP) as biomarker for
Comparison of salivary cortisol collection method “Salivette” versus “passive drool”
Continuously lower mean salivary cortisol concentrations in Salivettes than in plastic tubes were found independent of point of time or different day (data not shown).
The three-way repeated measures ANOVA showed statistically significant differences of salivary cortisol concentrations between the two saliva collection methods (F = 6.45; p = 0.032 and strong significant differences at six different points of time (F = 41.19; p < 0.0001) (Table 1), respectively. There was no significant difference
Discussion
Our study is the first to compare different saliva collection methods and to explore the relationship between salivary cortisol and total as well as calculated free serum cortisol concentrations with respect to the two collection devices used. The main finding of our study is that despite a lower cortisol concentration in Salivettes, salivary cortisol in Salivettes was the better predictor for TSC and FSC than salivary cortisol in plastic tubes. Salivettes were also the preferred method of
Acknowledgements
We thank Leo Heuts (Central Laboratory, RWTH–University Hospital Aachen) for the expert technical assistance and Diagnostic Systems Laboratories (Sinsheim, Germany) for providing us with reagents for the study.
References (13)
- et al.
Use of salivary biomarkers in biobehavioral research: cotton-based sample collection methods can interfere with salivary immunoassay results
Psychoneuroendocrinology
(2001) - et al.
Impact of saliva collection methods on sIgA and cortisol assays and acceptability to participants
J Immunol Methods
(2005) - et al.
Salivary testosterone determination in studies of child health and development
Horm Behav
(1999) - et al.
Assessing dehydroepiandrosterone in saliva: a simple radioimmunoassay for use in studies of children, adolescents and adults
Psychoneuroendocrinology
(1999) - et al.
Assessing estradiol in biobehavioral studies using saliva and blood spots: simple radioimmunoassay protocols, reliability, and comparative validity
Horm Behav
(2000) - et al.
Clinical use of unbound plasma cortisol as calculated from total cortisol and corticosteroid-binding globulin
J Steroid Biochem
(1987)