title: Accuracy of diagnostic tests for Cushing's syndrome: a systematic review and metaanalyses.
abstract: BACKGROUND
  The diagnosis of Cushing's syndrome (CS) requires the use of tests of unregulated hypercortisolism that have unclear accuracy.
  
  
  OBJECTIVE
  Our objective was to summarize evidence on the accuracy of common tests for diagnosing CS.
  
  
  METHODS
  We searched electronic databases (MEDLINE, EMBASE, Web of Science, Scopus, and citation search for key articles) from 1975 through September 2007 and sought additional references from experts.
  
  
  METHODS
  Eligible studies reported on the accuracy of urinary free cortisol (UFC), dexamethasone suppression test (DST), and midnight cortisol assays vs. reference standard in patients suspected of CS.
  
  
  METHODS
  Reviewers working in duplicate and independently extracted study characteristics and quality and data to estimate the likelihood ratio (LR) and the 95% confidence interval (CI) for each result.
  
  
  RESULTS
  We found 27 eligible studies, with a high prevalence [794 (9.2%) of 8631 patients had CS] and severity of CS. The tests had similar accuracy: UFC (n = 14 studies; LR+ 10.6, CI 5.5-20.5; LR- 0.16, CI 0.08-0.33), salivary midnight cortisol (n = 4; LR+ 8.8, CI 3.5-21.8; LR- 0.07, CI 0-1.2), and the 1-mg overnight DST (n = 14; LR+ 16.4, CI 9.3-28.8; LR- 0.06, CI 0.03-0.14). Combined testing strategies (e.g. a positive result in both UFC and 1-mg overnight DST) had similar diagnostic accuracy (n = 3; LR+ 15.4, CI 0.7-358; LR- 0.11, CI 0.007-1.57).
  
  
  CONCLUSIONS
  Commonly used tests to diagnose CS appear highly accurate in referral practices with samples enriched with patients with CS. Their performance in usual clinical practice remains unclear.
authors.affiliation: Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Mohamed B
authors.initials: MB
authors.lastname: Elamin
authors.forename: M Hassan
authors.initials: MH
authors.lastname: Murad
authors.forename: Rebecca
authors.initials: R
authors.lastname: Mullan
authors.forename: Dana
authors.initials: D
authors.lastname: Erickson
authors.forename: Katherine
authors.initials: K
authors.lastname: Harris
authors.forename: Sarah
authors.initials: S
authors.lastname: Nadeem
authors.forename: Robert
authors.initials: R
authors.lastname: Ennis
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Erwin
authors.forename: Victor M
authors.initials: VM
authors.lastname: Montori
mesh_terms: D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone; D006801:Humans; D006854:Hydrocortisone / Q000652:urine
chemical_list: D003907:Dexamethasone; D006854:Hydrocortisone