Production of gender-specific morning salivary cortisol reference intervals using internationally accepted procedures

Abstract

Salivary cortisol concentrations correlate well with biologically active unbound free plasma cortisol concentrations. Despite its practical and analytical advantages, salivary cortisol measurement has been used mainly as a research tool rather than for the routine evaluation of adrenal function. This may be partly explained by the lack of robust reference data in the literature. Using the recommended procedures for the production of reference intervals published by the International Federation of Clinical Chemistry, we aimed to produce morning salivary cortisol reference intervals for males and females. Salivary cortisol was measured in 496 specimens collected from 248 reference individuals (128 males, median age 41 years, range 16-86; and 120 females, median age 44 years, range 16-98) attending an otorhinolaryngology clinic. Reference individuals mailed saliva specimens sampled on two consecutive mornings to our laboratory, where cortisol concentrations were measured. Statistical analysis showed no significant correlation with age or body mass index. The following 95% gender-partitioned reference intervals were produced: males 10.9-40.3 nmol/l; and females 9.3-40.3 nmol/l. Knowledge of these salivary cortisol reference intervals helps us monitor the adrenal function of outpatients using topical intranasal glucocorticoids for rhinosinusitis.