Evaluation of an automated chemiluminescent immunoassay for salivary cortisol measurement. Utility in the diagnosis of Cushing's syndrome

Abstract

The aim of the current study was to validate an automated chemiluminescent immunoassay for cortisol quantification in saliva and to determine the cut-off level for Cushing´s Syndrome diagnosis in an adult population. The salivary cortisol levels from healthy individuals and patients previously diagnosed with Cushing´s Syndrome were measured with Siemens Immulite 2000 ® automatic chemiluminescent enzyme-immunoassay analyser with a brief modification. The limit of quantification was 3,4 nmol/L. The assay also demonstrated a high level of accuracy, as determined by linearity under dilution and recovery tests. Using this methodology, levels higher than 5.7 nmol/L is indicative of Cushing´s Syndrome with a diagnostic sensitivity and specificity of 90,5% and 97.4% respectively. The assay validated in the present study could be used in the clinical laboratories for the evaluation of cortisol levels in patients in which Cushing´s Syndrome is suspected.