title: Development and validation of a 0.5 mg dexamethasone suppression test as an initial screening test for the diagnosis of ACTH-dependent Cushing's syndrome.
abstract: For the diagnosis of Cushing' s syndrome (CS), the overnight 1 mg dexamethasone suppression test (DST) has been widely used as a standard low-dose DST. However, it is evident that 1 mg DST may not be sensitive enough to detect CS when the cortisol cut-off concentration is 5 microg/dL. Therefore, we developed and validated 0.5 mg DST as a new screening method for diagnosis of ACTH-dependent CS. To compare 0.5 mg DST with 1 mg DST, 110 patients with ACTH-dependent CS were enrolled, including 88 with Cushing' s disease (CD), 8 with subclinical CD and 14 with ectopic ACTH syndrome, as well as 134 control subjects. Subjects were given either 0.5 mg or 1 mg dexamethasone orally at 23:00 on different days, with blood samples collected the following morning between 8:00 and 9:00 to determine plasma cortisol concentration. The area under the receiver operator characteristics curve observing the 0.5 mg DST was higher than that of the 1 mg DST. The most sensitive and specific cut-off value of plasma cortisol concentration using 0.5 mg DST was found to be 3.05 microg/dL with 99.1% sensitivity and 98.4% specificity, identical to the 3 microg/dL cut-off currently used in the Japanese guideline for diagnosis of subclinical CD. In conclusion, 0.5 mg DST is a sensitive and specific screening test for diagnosis of ACTH-dependent CS. We recommend 0.5 mg DST with a cortisol cut-off concentration of 3 microg/dL to be used as the initial step in diagnosing ACTH-dependent CS.
authors.affiliation: Second Division, Department of Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan. okitaka@hama-med.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oki
authors.forename: Kozo
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hirata
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nigawara
authors.forename: Masaru
authors.initials: M
authors.lastname: Doi
authors.forename: Satoru
authors.initials: S
authors.lastname: Sakihara
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kageyama
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Suda
mesh_terms: D000182:ACTH Syndrome, Ectopic / Q000175:diagnosis; D000328:Adult; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone / Q000008:administration & dosage; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008875:Middle Aged; D047748:Pituitary ACTH Hypersecretion / Q000175:diagnosis; D012680:Sensitivity and Specificity
chemical_list: D003907:Dexamethasone; D006854:Hydrocortisone