CLINICAL RESEARCH ARTICLE doi:10.1210/clinem/dgaa269 J Clin Endocrinol Metab, August 2020, 105(8):e2807–e2814 https://academic.oup.com/jcem e2807 Late-Night Salivary Cortisol in Healthy, Community- Dwelling Asian Indians Assessed by Second- Generation ECLIA Nandini Prasad, 1 Puthiyaveettil Khadar Jabbar, 1 Chellamma Jayakumari, 1 Mathew John, 2 Retheesh Kollerazhikathu Haridasan, 3 Thekkumkara Surendran Nair Anish, 3 Ramesh Gomez, 1 Darvin Vamadevan Das, 1 Ravindranath Sreenath, 1 Geena Susan George, 1 and Abilash Nair 1 1 Department of Endocrinology & Metabolism, Government Medical College Thiruvananthapuram, Thiruvananthapuram, Kerala 695011, India; 2 Providence Endocrine and Diabetes Specialty Centre, Thiruvananthapuram, Kerala 695011, India; and 3 Department of Community Medicine, Government Medical College Thiruvananthapuram, Thiruvananthapuram, Kerala 695011, India ORCiD numbers: 0000-0001-6133-8281 (N. Prasad); 0000-0001-6382-2798 (P. K. Jabbar); 0000-0002-1811-9769 (C. Jayakumari); 0000-0002-6435-7995 (M. John); 0000-0002-6957-5895 (T. S. Anish); 0000-0003-4230-710X (G. S. George); 0000-0001-6776-1582 (A. Nair). Background: Late-night salivary cortisol (LNSC) is used as a screening test for Cushing syndrome (CS), but there is no community-derived normative data for the normal upper limit in the South Asian population. This study aimed to determine the upper limit of normal (97.5th percentile) for LNSC in an Asian Indian population using a commercially available second-generation electrochemiluminiscence immunoassay (ECLIA). Methods: LNSC in apparently healthy community-dwelling individuals was assessed by multistage cluster sampling. Healthy individuals age 18 to 60 years from 8 urban and 8 rural clusters of Thiruvananthapuram district were studied. Thirty people from an approximate population of 1000 individuals from each cluster participated in the study. A saliva sample was collected between 11 PM and 12 midnight and analyzed using Roche COBAS-e-411 and ultrasensitive Cortisol II kits the next day. Results: Cortisol values from 474 salivary samples were available for fnal analysis after exclusion of improperly collected samples. The 97.5th percentile of the LNSC concentrations was 0.25 μg/dL (6.89 nmol/L) (90% CI, 0.23-0.27 μg/dL; ie, 6.34-7.45 nmol/L). In postmenopausal women, median LNSC was signifcantly higher but the 90% CI for the upper limit of their LNSC (0.28μg/dL or 7.72 nmol/L) overlapped with that of premenopausal women. Conclusions: This study establishes the normal value of LNSC estimated by second-generation ECLIA in healthy community-dwelling Asian Indian individuals for the frst time. Salivary cortisol at 11 PM to 12 AM is less than 0.25μg/dL (6.89 nmol/L) in the general Asian Indian population. Menopause causes a signifcant increase in LNSC and may lead to overdiagnosis of CS if not interpreted carefully. (J Clin Endocrinol Metab 105: e2807–e2814, 2020) Freeform/Key Words: late-night salivary cortisol (LNSC), Cortisol II, Cushing syndrome, Asian Indian, ECLIA, menopause Abbreviations: ASHA, accredited social health activist; AW, Anganwadi area; BMI, body mass index; CI, Confdence Interval; CS, Cushing syndrome; FWC, family welfare clinic area; IQR, interquartile range; LNSC, late-night salivary cortisol; SD, Standard Deviation. ISSN Print 0021-972X ISSN Online 1945-7197 Printed in USA © Endocrine Society 2020. All rights reserved. For permissions, please e-mail: journals. permissions@oup.com Received 25 March 2020. Accepted 8 May 2020. First Published Online 19 May 2020. Corrected and Typeset 10 June 2020. Downloaded from https://academic.oup.com/jcem/article/105/8/e2807/5840379 by guest on 07 September 2022