title: The diagnostic standard of preclinical Cushing's syndrome: evaluation of the dexamethasone suppression test using various cortisol kits.
abstract: Incidental discovery of an adrenal mass, the so-called adrenal incidentaloma, has been increasing due to the advances in non-invasive diagnostic imaging tools. The criteria of diagnosis for preclinical Cushing's syndrome (preCS) in Japan were made by Nawata et al. supported by the Ministry of Health and Welfare in 1995. The results of suppression of cortisol by dexamethasone (DEX) (plasma cortisol above 3 microg/dl after 1 mg of DEX and above 1 microg/dl after 8 mg of DEX) are essential for the diagnosis of preCS due to an adrenal adenoma. However, plasma cortisol levels after the two doses of DEX suppression tests were found to be discrepant and repeated DEX suppression tests sometimes yielded different results. Therefore, we examined the cortisol values of DEX suppression tests in patients with preCS using four different cortisol assay kits: Amerlex cortisol kit (AMA), SPAC-S cortisol kit (SPA), ADVIA-Centaur cortisol assay (ADV) and ECLusys 2010 cortisol assay (ECL). The diagnosis for preCS was done using the AMA kit. Correlation between the kits was good. However, cortisol levels measured by SPA, ADV and ECL were lower than those measured by AMA. In the 1 mg DEX test, the cortisol levels measured with the SPA, ADV and ECL kits were suppressed in 2 patients with preCS. With 8 mg of DEX, cortisol levels measured with the SPA and ADV kits were suppressed in 2 patients with preCS. The diagnosis of preCS is decided by the cortisol kit used, but the cortisol levels differ among the kits. It is suggested that the lack of the standardization of cortisol measurement is one of the causes of confusion in the diagnosis of preCS.
authors.affiliation: Central Clinical Laboratories, Department of Clinical Laboratory, Tokyo Women's Medical University School of Medicine, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Odagiri
authors.forename: Mitsuhide
authors.initials: M
authors.lastname: Naruse
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Terasaki
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Kazuko
authors.initials: K
authors.lastname: Jibiki
authors.forename: Sachiko
authors.initials: S
authors.lastname: Takagi
authors.forename: Masayo
authors.initials: M
authors.lastname: Tanabe
authors.forename: Kazue
authors.initials: K
authors.lastname: Takano
mesh_terms: D000368:Aged; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone; D005260:Female; D005938:Glucocorticoids; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic / Q000592:standards*
chemical_list: D005938:Glucocorticoids; D011933:Reagent Kits, Diagnostic; D003907:Dexamethasone; D006854:Hydrocortisone