Clinical applications of the dexamethasone suppression test for endogenous depression

The dexamethasone suppression test (DST) was developed from the neuroendocrine research strategy to provide indirect information about the integrity of the limbic system in patients with endogenous depression (ED). Abnormal test results occur in close temporal relationship to clinical episodes of ED, but not during the intervals between episodes. The neuroendocrine disinhibition revealed by the test is not a trait marker of individuals predisposed to develop ED. A standardized DST procedure has been established and can be applied in outpatient or inpatient routine clinical practice, with good sensitivity (50-65%) and high specificity (96%). The conditional probability principles of interpreting the test results are discussed and the effect of prevalence on the predictive value of the test results is emphasized. The DST should not be used as a screening test for all psychiatric patients but should be reserved for cases where clinical indications for its use are present. These indications include diagnostic confirmation of ED, monitoring the response to treatment, prediction of relapse or new episodes, and possibly prediction of suicide risk in patients with ED. The test may be especially useful in the diagnostic assessment of patients with difficult or confusing presentations of ED such as catatonia, depressive pseudodementia, depression in adolescents or children, "masked" depression, depression complicated by a personality disorder, and schizoaffective depression.