Serum cortisol correlates strongly with salivary cortisol and cortisone in girls and boys, and across all ages

Olivia Buckingham-Woodhouse; Julie Park; Brian Keevil; Jo Adaway; Daniel Hawcutt; Charlotte Elder**; Joanne Blair**

Background: Cortisol (SerC) is generally measured in serum. However, blood tests require attendance at a healthcare provision and can be distressing and inconvenient. Cortisol (SC) and cortisone (SCn) can be measured in saliva. Saliva sampling is patient-friendly, minimally invasive and can be performed at home. We present correlations between paired SC and SCn and SerC measurements in a large paediatric cohort.

Methods: Paired serum and saliva samples were collected from healthy volunteers and children undergoing a Short Synacthen Test (SST). The relationship between baseline SerC and SC and SCn was analysed by Spearman’s Rho correlation for the whole group and then by age and sex. Females aged <8 and males <9 years were considered prepubertal. Females aged >14 and males >15 years were considered post pubertal.

Results: 122 participants (59F), median age 11.4 years (range=3.0-18.8) were included; 43 healthy volunteers (Alder Hey Children’s Hospital) and 79 children attending for SST (Sheffield Children’s Hospital). Six participants were excluded due to missing data or insufficient samples, and one due to suspected hydrocortisone contamination of saliva. One participant had missing SC data. The correlation between SerC and SC and SCn was +0.726 [0.623-0.805], P <0.001 (114 paired samples) and +0.716 [0.610-0.797], P <0.001 (115 paired samples) respectively.

Table 1: Spearman’s Rho correlation by gender, age, and pubertal status. * P <0.05
	Serum cortisol and SC	Serum cortisol and SCn
Females (n = 54)	+0.716 [0.549-0.828]*	+0.770 [0.628-0.863]*
Males (n = 61)	+0.704 [0.524-0.815]*	+0.647 [0.466-0.776]*
Pre-pubertal (n = 24)	+0.591 [0.224-0.811]*	+0.614 [0.268-0.820]*
Pubertal (n = 72)	+0.713 [0.224-0.811]*	+0.694 [0.546-0.800]*
Post-pubertal (n = 19)	+0.623 [0.221-0.844]*	+0.598 [0.183-0.832]*
Age 3-6 (n = 13)	+0.640 [0.086-0.892]*	+0.779 [0.383-0.933]*
Age 7-10 (n = 33)	+0.438 [0.101-0.685]*	+0.520 [0.204-0.737]*
Age 11-14 (n = 53)	+0.767 [0.622-0.862]*	+0.704 [0.530-0.821]*
Age 15-18 (n = 16)	+0.692 [0.284-0.888]*	+0.671 [0.248-0.879]*

Conclusion: To our knowledge, this is the first time the correlation between SerC and SC and SCn has been examined in a diverse paediatric cohort. Females demonstrated stronger correlations than males, with the strongest correlation between SerC and SCn. The correlation was strongest in children aged 11-14 years and lowest in those aged 7-10 years. Our findings are similar to associations demonstrated in adult cohorts previously. Further analyses in larger cohorts are required to confirm whether age and sex related differences are clinically meaningful. These data provide further evidence in support of the use of saliva in adrenal function testing as a non-invasive more patient-centred approach.

**Charlotte Elder and Joanne Blair contributed equally to this work.

ESPE Abstracts

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