Clinical utility of the dexamethasone suppression test assessed by plasma and salivary cortisol determinations

Concentrations of cortisol in saliva and plasma were compared in matched samples during a standard 1 mg dexamethasone suppression test. The study involved 185 routine psychiatric admissions, all of whom were classified according to DSM-III criteria. In a group of 122 matched samples of saliva and plasma, there was a Pearson correlation coefficient of 0.867 and a Spearman rank correlation coefficient of 0.869. Medication with anticholinergic side effects had little effect on the correlation and was not associated with major difficulties in salivary sampling due to "dry mouth." In a group of 178 diagnoses where both saliva and plasma were obtained, results were almost identical. Although nonsuppression was found in all psychiatric conditions, there was a very significant association with major depressive episode with melancholia.