title: Assessment of the utility of the high-dose dexamethasone suppression test in confirming the diagnosis of Cushing disease.
abstract: OBJECTIVE
  To determine the utility of high-dose dexamethasone suppression (HDDS) tests to confirm the diagnosis of Cushing disease (CD).
  
  
  METHODS
  In this retrospective study, we reviewed medical records of patients who underwent either the overnight 8-mg HDDS test or the 2-day 2-mg HDDS test every 6 hours. The percentage suppression of morning serum cortisol and the percentage suppression of 24-hour urine free cortisol (UFC) were calculated.
  
  
  RESULTS
  Of 141 patients with proven CD who underwent HDDS tests, 77 (55%) underwent the overnight 8-mg HDDS test and 64 (45%) underwent the 2-day 2-mg HDDS test every 6 hours. With the overnight 8-mg HDDS test, 73 of 77 patients (95%) had greater than 50% suppression and 48 of 77 patients (62%) had greater than 80% suppression of the morning serum cortisol in comparison with the baseline value. With the 2-day 2-mg HDDS test, only 41 of 64 patients (64%) had greater than 90% suppression of 24-hour UFC.
  
  
  CONCLUSIONS
  We conclude that the overnight 8-mg HDDS test accurately confirmed the diagnosis of CD with a high sensitivity of 95% with use of a criterion of greater than 50% suppression; in contrast, the sensitivity was only 62% with use of a more precise cutoff of greater than 80% suppression. The 2-day 2-mg HDDS test with a criterion of greater than 90% suppression of 24-hour UFC had a sensitivity of 64%. These results confirm the limited precision of the HDDS tests.
authors.affiliation: Department of Endocrinology, Crystal Run Healthcare, Middletown, New York, USA. saytug@crystalrunhealthcare.com
authors.forename: Serhat
authors.initials: S
authors.lastname: Aytug
authors.forename: Edward R
authors.initials: ER
authors.lastname: Laws
authors.forename: Mary Lee
authors.initials: ML
authors.lastname: Vance
mesh_terms: D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D000328:Adult; D015331:Cohort Studies; D003907:Dexamethasone / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D005938:Glucocorticoids / Q000008:administration & dosage; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism / Q000652:urine; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D047748:Pituitary ACTH Hypersecretion / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology / Q000652:urine; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone; D006854:Hydrocortisone