Detection of salivary cortisol at two different time points at night

Abstract

Objective To compare the detection results of salivary cortisol(SL) at 23:00 and 24:00 to estimate whether the collection of saliva can be taken in advance at 23:00 for the screening and diagnosis of Cushing's syndrome(CS).Methods Saliva samples were collected by a cotton-based sampling approaches Salivettes at 23:00 and 24:00 from 108 normal subjects (NS group),50 patients (NCS group) with type 2 diabetes,primary hypertension or non-functional adrenal adenoma and 7 patients with Cushing' s syndrome(CS group).Then the samples were assayed by ELISA.Results The levels of SC at 23:00 (SC23) and 24:00 (SC24) in different groups were:2.01 ± 0.91 ng/ml,1.96 ± 0.85 ng/ml in NS group,3.55 ± 1.17 ng/ml,3.81 ± 1.49 ng/ml in NCS group,and 12.63 ± 6.14 ng/ml,10.98 ± 3.98 ng/ml in CS group (all P＞0.05).Using Pearson correlation analysis,SC23 and SC24 showed a very good linear correlation (r =0.924,P＜ 0.001).SC23 or SC24 in CS group were obviously higher than NS and NCS group.The areas under the ROC curves of SC23 and SC24 were 0.995 and 0.996 respectively,which displayed good accuracy to diagnosis of CS.Conclusions Midnight salivary cortisol is a convenient and sensitive indicator for the screening and diagnosis of CS.The concentrations of salivary cortisol at 23:00 and 24:00 are close,so collecting saliva at 23:00 is feasible for the clinical screening and diagnosis of CS. Key words: Salivary cortisol(SC) ; Cushing's Syndrome (CS) ; ELISA