Late-night salivary cortisol (LNSaC) is an easy-to-use test reflecting the free cortisol level in the serum and does not require hospitalization. Controlled studies reported that LNSaC has a high sensitivity and specificity, but have not set a clearly defined cut-off value to be used in the diagnosis of Cushing’s syndrome. In this study, we aimed to evaluate the diagnostic performance of LNSaC in patients with clinical Cushing’s syndrome (CCS) and subclinical Cushing’s syndrome (SCS). The data of 543 patients, whose LNSaC levels were assessed using electrochemiluminescence immunoassay method, were retrospectively evaluated. The study included a total of 324 patients: 58 patients with CCS, 53 patients with SCS, and 213 patients without Cushing’s syndrome (NoCS). The cause of the Cushing’s syndrome was hypophyseal in 26 patients (45%), adrenal in 24 patients (41%), and ectopic in 8 patients (14%) in the CCS group. Median LNSaC levels were 0.724 (0.107–33) µg/dL in CCS group, 0.398 (0.16–1.02) µg/dL in SCS group, and 0.18 (0.043–0.481) µg/dL in NoCS group (p=0.001). Accordingly, LNSaC had 89.6% sensitivity and 81.6% specificity at a cut-off value of 0.288 µg/dL in the diagnosis of CCS; and had 80.7% sensitivity and 85.1% specificity at a cut-off value of 0.273 µg/dL in the diagnosis of SCS. In the present study, a lower sensitivity and specificity than previously reported was found for LNSaC in the diagnosis of CCS. Moreover, the diagnostic performance of LNSaC in patients with SCS was close to its diagnostic performance in patients with CCS. Each center should determine its own cut-off value based on the method adopted for LNSaC measurement, and apply that cut-off value in the diagnosis of Cushing’s syndrome.
- adrenal cortex hormones
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Contributors NY, RS: substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; drafting the work or revising it critically for important intellectual content; final approval of the version to be published and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. GT, HB, SÖ: substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work. HAA, MKB: drafting the work or revising it critically for important intellectual content.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Akdeniz University.
Provenance and peer review Not commissioned; externally peer reviewed.
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