Determination of salivary cortisol by ELISA and its application to the assessment of the circadian rhythm in children.

In 35 young children, circadian rhythms of salivary cortisol levels were determined by ELISA using a commercially available kit with a minor modification. The concentration of labeled cortisol in the serum kit was reduced in order to measure cortisol in 10 microliters of saliva. Intra- and interassay coefficients of variation for salivary cortisol ranged from 2.4 to 9.9 and 3.2 to 8.9%, respectively. Recovery of salivary cortisol was 82.9-107.0%. There was a highly significant correlation between cortisol levels in saliva and serum in adults (r = 0.857). Salivary cortisol levels ranged from 0.01 to 2.252 micrograms/100 ml and showed significant diurnal variation in the children. Our ELISA is a precise, simple, noninvasive and useful method for clinical practice and study in infants and children.