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J Endocrinol Invest. 2019 Mar;42(3):327-335. doi: 10.1007/s40618-018-0921-1. Epub 2018 Jul 9.

The diagnostic accuracy of increased late night salivary cortisol for Cushing's syndrome: a real-life prospective study.

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Endocrinology Unit, Department of Medicine DIMED, University-Hospital of Padova, Via Ospedale Civile, 105, 35128, Padua, PD, Italy.
Division of Endocrinology, Department of Clinical and Molecular Sciences (DISCLIMO), Umberto I Hospital, Polytechnic University of Marche, Via Tronto 10B, 60020, Torrette, AN, Italy.



A prompt diagnosis of Cushing's Syndrome (CS) in high-risk populations is mandatory: 1-mg dexamethasone suppression test (1-mg DST), late night salivary cortisol (LNSC), and urinary-free cortisol (UFC) are recommended, despite thresholds calculated in retrospective studies. Our aim was to study the diagnostic accuracy of LNSC measured with chemiluminescence assay in a prospective study, confirming discrepancies with mass spectrometry (MS).


We enrolled 117 controls and 164 suspected CS (CS = 47, non-CS = 117). In case of increased LNSC, high clinical suspicion of CS or adrenal incidentaloma, patients were hospitalized to exclude/confirm CS.


LNSC levels were higher in patients with suspected CS, CS, and non-CS than controls. Considering 16 nmol/L as threshold for CS, overall LNSC revealed SE 97% and SP 84% in the whole group of subjects considered, achieving positive/negative likelihood ratio of 5.56/0.045, respectively. 35 out of 81 subjects with increased LNSC were non-CS (15 diabetic and 20 obese): considering only those patients with increased likelihood to have a CS (the non-CS patients) SP decreased to 70%, and further reduced to 60% if we discharged subjects with adrenal incidentaloma. MS analyses reduced partially the number of false-positive LNSC.


LNSC measured in automated chemiluminescence is reliable in clinical practice: it present a high diagnostic accuracy to exclude hypercortisolism in patients with normal cortisol levels. MS could be used to reduce the number of false-positive results; nevertheless, some non-CS subjects with functional hypercortisolism could have a mild impairment of cortisol rhythm.


Cushing’s syndrome; Diagnosis; Late night salivary cortisol; Liquid chromatography–tandem mass spectrometry

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