The dexamethasone suppression test for the detection, diagnosis, and management of depression consists of two steps. Dexamethasone is administered orally, 1 mg in tablet form, at 2300 h. Then, samples of venous blood are drawn at 0800 h, 1600 h, and 2300 h the following day; in outpatients, only a 1600 h venous blood sample commonly is obtained.
A serum cortisol level greater than 4.5 to 5 µg/dL for any of the blood samples is abnormal and represents a positive test, depending on the assay used (1). Thus, it is important that the laboratory method used be precise and accurate