Neuroendocrine aspects of primary endogenous depression: VI. Receiver operating characteristic analysis of the cortisol suppression index versus the dexamethasone suppression test in patients and matched controls.

The cortisol suppression index (CSI), which is the ratio of the predexamethasone (DEX) serum cortisol concentration to the post-DEX cortisol concentration, has been investigated as an alternative means of analyzing the response of the hypothalamo-pituitary-adrenal axis to DEX. We used receiver operating characteristic (ROC) analysis to examine the CSI versus the corresponding standard post-DEX cortisol values in a sample of 40 primary endogenous major depressives versus 40 matched normal control subjects who underwent a DEX suppression test (DST). The CSI was highly correlated with post-DEX cortisol values and showed no advantage in test performance over the standard DST across a wide range of criterion values. ROC analysis is a useful technique for determining the utility of the DST and other biological markers in psychiatry.