Introduction: Salivary cortisol measurement is a non-invasive and easy test to carry out. It is painless and does not cause stress.
Aim: The aim of the present study was to evaluate the correlation between salivary cortisol (SaC) and serum cortisol (SeC) after 1 mg Dexamethasone (DXM) overnight and their diagnostic utility as screening test of Cushings syndrome (CS).
Methods: We performed a prospective study in 92 patients with CS suspicion. Samples of saliva and peripheral blood were collected at 08:00h after oral administration of 1mg of DXM overnight (23:00h). CS diagnosis was confirmed in 10 patients. Salivary and serum cortisol measurements were performed by electrochemiluminscent immunoassay (ECLIA) method on an automated Cobas 8000 (Roche®). To analyze the correlation between SaC and SeC we used the Passing-Bablock nonparametric linear regression test with the statistical package Medcalc®. To calculate the sensitivity-specificity of SeC we used the stablished 1.8 mcg/dL cut-off value. To calculate the best cut-off point of SaC we used the Receiver Operating Characteristic (ROC) curves.
Results: There was a significant correlation between salivary and serum cortisol after 1 mg of DXM overnight, (r=0.634; P<0.001). The estimated cut-off point for SaC was 0.08 μg/dL. The sensitivity, specificity, PPV and NPV of this cut-off were: 60%, 82.93%, 18.18% and 93.22%, respectively. The sensitivity, specificity, PPV and NPV of 1.8 μg/dL cut-off point of SeC were 70%, 57.32%, 16.67% and 94% respectively.
Conclusion: If these results are reproduced in an independent and bigger sample, the measurement of salivary cortisol after 1 mg of DXM overnight could substitute the classical Nugents test in the screening of Cushings syndrome.
18 - 21 May 2019
European Society of Endocrinology