Late-night and low-dose dexamethasone-suppressed cortisol in saliva and serum for the diagnosis of cortisol-secreting adrenal adenomas

ObjectiveIn patients with adrenal incidentalomas, hormonally active masses need to be considered, particularly cortisol-producing adenomas (CPA), aldosterone-producing adenomas, and pheochromocytomas. The screening for hypercortisolism relies on confirming excess cortisol secretion and insufficient suppression after dexamethasone. Because of its high correlation with free cortisol and its stress-free collection, salivary cortisol (SaC) may offer advantages over serum cortisol (SeC). We evaluated the value of SaC and SeC for the diagnosis of CPA.DesignComparative study between 2001 and 2006.MethodsThirty-eight patients with confirmed CPA were compared with 18 healthy subjects as well as 48 control patients suffering from aldosterone-producing adenomas (n=13), pheochromocytomas (n=16), or nonfunctioning adenomas (n=19). Sampling of saliva and serum was performed at 2300 and at 0800 h following low-dose dexamethasone suppression. Receiver operating characteristics analysis was used to calculate thresholds with at least 95% sensitivity for CPA.ResultsRegarding the cutoffs for late-night cortisol, SaC (4.8 nmol/l, sensitivity 97%, specificity 69%) was slightly more specific than SeC (115 nmol/l, sensitivity 97%, specificity 63%). In contrast, the cutoff for dexamethasone-suppressed SaC (3.7 nmol/l, sensitivity 97%, specificity 83%) was slightly less specific than SeC (94 nmol/l, sensitivity 97%, specificity 88%). However, the latter cutoffs demonstrated greater specificity when compared with the cutoffs for late-night cortisol.ConclusionThe diagnostic accuracy of SaC is as good as SeC. Owing to its higher specificity, dexamethasone-suppressed cortisol is preferable to late-night cortisol when screening for Cushing's syndrome in patients with adrenal incidentalomas.