Selection Of Midnight Salivary Cortisol Detection Time And Establishment Of Normal Reference Range

Objective:By applying the methods of measuring plasma cortisol(PC)and salivary cortisol(SC)currently used in our laboratory,the reference range of the normal value of salivary cortisol in our laboratory at midnight was preliminarily determined,and the appropriate detection time of salivary cortisol and serum cortisol in our laboratory at midnight was selected.Methods:A total of 110 healthy volunteers,aged between 18 and 65,were selected from the Department of Endocrinology of Xinjiang Uygur Autonomous Region People’s Hospital from October 2019 to November 2020.The subjects were divided into male(n=24)and female(n=96)according to different sexes.Serum and salivary cortisol of the subjects were collected at 24:00 and 2:00 Beijing time and 8:00 Beijing time the next morning.Sc was determined by chemiluminescence assay,and PC was determined by chemiluminescence immunoassay(CLIA).Sc was determined by chemiluminescence assay,and PC was determined by chemiluminescence immunoassay(CLIA).At the same time,age,weight,height,BMI,hip circumference and waist circumference of healthy volunteers were measured.The normal reference range of salivary cortisol(SC)concentration was preliminarily discussed,and the selection of salivary cortisol detection time at midnight was analyzed.Results:The normal reference ranges of 8:00,24:00,2:00 for SC and PC were:SC:0.48～1.32(ug/dL),0.04～0.25(ug/dL),0.04～0.22(ug/dL),PC:12.24～24.53(ug/dL),1.63～5.42(ug/dL),1.17～4.95(ug/dL),There was no significant difference in salivary cortisol between 24:00 and 2:00(P>0.005).The difference in serum cortisol detection results was statistically significant,which indicated that serum cortisol could reach its lowest point at 2:00,which was consistent with our prediction that the cortisol rhythm in this region would shift back due to the time difference between regions.Therefore,the midnight serum cortisol detection time in this region was selected 2:00 is more appropriate,and the salivary cortisol detection time is both 24:00 and 2:00,while saliva collection at 24:00,most of the subjects are awake,easy to obtain enough samples,and patients are more likely to accept,compliance is better.Therefore,the detection time of salivary cortisol can be selected as 24:00.Conclusion:There was no statistical difference in the saliva cortisol test results of healthy volunteers at 24:00 and 2:00,so saliva can be collected at both 24:00 and 2:00,and the international standard time of 24:00 can be used to collect saliva cortisol in this area.The difference between 24:00 and 2:00 in serum cortisol of healthy volunteers was statistically significant,and 2:00 was lower than 24:00.Therefore,2:00 was a more appropriate time for midnight serum cortisol detection in this area.