OVERNIGHT DEXAMETHASONE SUPPRESSION TEST - COMPARISON OF PLASMA AND SALIVARY CORTISOL MEASUREMENT FOR THE SCREENING OF CUSHINGS-SYNDROME

The overnight 1-mg dexamethasone suppression test is a very good scree ning test for subjects suspected of having Gushing's syndrome. To simp lify the procedure, we evaluated the 1-mg dexamethasone suppression te st with measurement of salivary cortisol. We performed this test with plasma and salivary cortisol measurements in 27 patients with Gushing' s syndrome and 64 normal controls. The sensitivity and specificity of plasma cortisol measurements were 100% and 87%, respectively, for a cu t-off point of 100 nmol/l, in accordance with previous studies. The re sults of salivary cortisol showed the absence of overlap between the t wo groups, with a sensitivity and specificity of 100% for a cut-off po int of 2.8 nmol/l. On a larger series, however, one might occasionally miss the diagnosis of a patient with Gushing's syndrome. Therefore, w e favor a cut-off point of 1.9 nmol/l, the sensitivity remaining at 10 0% and the specificity being 94%. In conclusion we recommend the overn ight dexamethasone suppression test with measurement of salivary corti sol as a screening test for Gushing's syndrome.