Clinical accuracy of midnight salivary cortisol measured by automated electrochemiluminescence immunoassay method in Cushing's syndrome

Abstract

Background: The diagnosis of Cushing's syndrome (CS) represents a challenge for endocrinologists. Several screening tests are used, but none of them seems to be the gold standard for the diagnosis. The aim of this study was to confirm the diagnostic value of salivary cortisol (SC) as a first-level screening test and to evaluate the clinical performance of a electrochemiluminescence immunoassay (ECLIA) method. Methods: In 33 patients with a strong clinical suspicion of CS, we evaluated urinary free cortisol, circadian rhythm plasma cortisol (PC) and morning PC after low-dose dexamethasone suppression test (LDDST). At the same sampling times, we evaluated SC analysed by the same automated method. Correlation studies were evaluated by Spearman index (significance P , 0.05). Results: On the basis of biochemical results CS was confirmed in 21/33. SC was significantly correlated to PC at 12:00 and 23:00. Thus, we chose 8.3 nmol/L as midnight SC cut-off value with 100% sensitivity and 97.4% specificity. The cut-off chosen after LDDST was 1.7 nmol/L (100% sensitivity and 72% specificity). Conclusion: SC assay showed a good clinical accuracy and the ECLIA method can be used in clinical routine to obtain fast results easily.

Cushing’s syndrome: diagnosis and surveillance using salivary cortisol

“…Immunoassays include the radioimmunoassay (RIA), enzyme-linked immunosorbant assay (ELISA), and automated chemiluminescence and fluorometric detection assays [11][12][13][14][15][16][17][18][19][20]. Although the detection method and automaticity of these methods vary, they are all essentially competitive binding assays using a primary antibody raised against a conjugated form of cortisol.…”

Assessment of salivary free cortisol levels by liquid chromatography with tandem mass spectrometry (LC-MS/MS) in patients treated with mitotane

“…Finally, SC sampling is promising as samples are easy to obtain: this procedure does not require hospitalization and samples are stable up to 7 days at room temperature, and up to 1 month or more at 4°C. 19 SC reflects a free fraction of plasma cortisol and may thus be employed for a more accurate evaluation of patient monitoring during mitotane treatment. Indeed, salivary cortisol concentrations reflect unbound plasma cortisol concentrations and are therefore generally unaffected by variations in CBG values.…”

Diagnostics of hypercortisolism — comparison between the clinical usefulness of salivary and serum cortisol measurements

“…Differences between presented results may be explained by different diagnostic criteria for SCS and different assay methods used. Salivary cortisol has been usually measured by RIA and ELISA [18,19,23,25,26] and much more rarely by electrochemiluminescent immunoassay (ECLIA) or liquid chromatography tandem mass spectrometry (LC-MS/ /MS) [23,27,28]. The study by Beko et al revealed better performance of LSC using ECLIA (sensitivity 100% and specificity 88%) compared to RIA (sensitivity 100% and specificity 71%) [23].…”