A modified dexamethasone suppression test for endogenous depression

In order to simplify the dexamethasone suppression test (DST), we have administered a lower dosage of dexamethasone (DEX) and shortened the sampling time to a single morning blood sample. DEX (in dosage increments from 0.125 to 1.0 mg, p.o.) was administered at 2300 h to normal volunteers in a double-blind randomized fashion, and blood samples were taken at 0700 h the following morning. While significant cortisol suppression occurred after the 0.375 mg, 0.5 mg, and 1.0 mg doses of DEX, the 0.5 mg dose was the smallest that clearly suppressed cortisol in all eight subjects. This dose then was used to test the feedback sensitivity of the central nervous system (CNS)-pituitary-adrenal axis in endogenously depressed patients. Twenty endogenously depressed patients and 20 normal volunteers were given both the standard 1.0 mg DST, with post-DEX serum cortisol determined at 1500 h, and the simplified 0.5 mg DST, with post-DEX serum cortisol determined at 0700 h. Four patients (20%) and one control (5%) were nonsuppressors after the 1.0 mg DST, and nine patients (45%) and one control (5%) were nonsuppressors after the 0.5 mg DST. In addition, nine patients with major depression (nonendogenous subtype) and 15 patients with panic attacks also were studied using the 0.5 mg DST. Only 2 of these 24 patients (8%) were nonsuppressors. The results suggest that the single-sample 0.5 mg DST is more sensitive than the standard 1.0 mg DST, and the specificity of the modified test appears comparable to the standard form of the test.