Diagnostics of hypercortisolism - Comparison between the clinical usefulness of salivary and serum cortisol measurements

Abstract

Introduction: The aim of this study was the comparison of 24h urine free cortisol (UFC), serum cortisol at 11pm (SCM) and late-night salivary cortisol (LSC) in patients suspected for hypercortisolism, and an assessment of the usefulness of these measurements in diagnosing overt Cushing's (OCS) syndrome, pseudo Cushing's state (PCS) and subclinical Cushing's syndrome (SCS). Material and methods: The study group consisted of 82 patients, of whom four patients had SCS, three OCS and eight PCS. For measurements of LSC, the ELISA method was used, and for UFC and SCM determination, chemiluminescent microparticle immunoassay was used. Results: The highest correlation coefficient characterised LSC and SCM (r = 0.72). Area under curve (AUC) for SCM and LSC in receiver operating characteristic (ROC) for OCS was: 0.86 v. 0.74; for PCS: 0.83 v. 0.70; and for SCS: 0.74 v. 0.79. Conclusions: Our findings suggest that LSC is more useful compared to SCM in diagnosing subclinical Cushing's syndrome. Moreover, LSC seems to be a valuable diagnostic criterion to distinguish pseudo Cushing's state. However, to obtain reliable cut-offs for LSC values, a larger group of hypercortisolic patients is needed.