Objective: The use of late-night salivary cortisol (LNSalC) for diagnosing subclinical hypercortisolism (SH) is debated. No data are available regarding the role of LNSalC as measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in SH diagnosis. The aim of this study was to evaluate the diagnostic accuracy of LNSalC measured by LC-MS/MS in SH.
Design: Cross-sectional prospective study of outpatients.
Methods: In 70 consecutive patients with adrenal incidentalomas (AI), without signs and symptoms of hypercortisolism, we diagnosed SH in the presence of at least two of the following: cortisol after 1 mg overnight dexamethasone suppression test (1 mg DST) >83 nmol/l, 24-h urinary free cortisol (UFC) >193 nmol/24 h, and morning ACTH <2.2 pmol/l. The LNSalC levels by LC-MS/MS at 2300 h (normal values <2.8 nmol/l) and the presence of hypertension, type 2 diabetes mellitus (T2DM), and osteoporosis (OP) were assessed.
Results: The increased LNSalC levels (>2.8 nmol/l) had an 83.3% specificity (SP) and a 31.3% sensitivity (SN) for predicting the biochemical diagnosis of SH. The increased LNSalC had an 85.2% SP and a 55.6% SN for predicting the presence of hypertension, T2DM, and OP, while the combination of LNSalC >1.4 nmol/l (cutoff with 100% SN) plus 1 mg DST >50 nmol/l had an 88.9% SN and an 85.2% SP (similar to SH criterion at enrollment).
Conclusions: In AI patients, LNSalC measured by LC-MS/MS appears to be useful in combination with 1 mg DST for diagnosing SH, while it is not useful as a single criterion.