title: Multicenter performance evaluation of a second generation cortisol assay.
abstract: BACKGROUND
  Untreated disorders of the adrenocortical system, such as Cushing's or Addison's disease, can be fatal, and accurate quantification of a patient's cortisol levels is vital for diagnosis. The objective of this study was to assess the analytical performance of a new fully-automated Elecsys® Cortisol II assay (second generation) to measure cortisol levels in serum and saliva.
  
  
  METHODS
  Four European investigational sites assessed the intermediate precision and reproducibility of the Cortisol II assay (Roche Diagnostics) under routine conditions. Method comparisons of the Cortisol II assay vs. liquid chromatography-tandem mass spectrometry (LC-MS/MS), the gold standard for cortisol measurement, were performed. Cortisol reference ranges from three US sites were determined using samples from self-reported healthy individuals.
  
  
  RESULTS
  The coefficients of variation (CVs) for repeatability, intermediate precision, and reproducibility for serum samples were ≤2.6%, ≤5.8%, and ≤9.5%, respectively, and for saliva were ≤4.4% and ≤10.9%, and ≤11.4%, respectively. Agreement between the Cortisol II assay and LC-MS/MS in serum samples was close, with a slope of 1.02 and an intercept of 4.473 nmol/L. Reference range samples were collected from healthy individuals (n=300) and serum morning cortisol concentrations (5-95th percentile) were 166.1-507 nmol/L and afternoon concentrations were 73.8-291 nmol/L. Morning, afternoon, and midnight saliva concentrations (95th percentile) were 20.3, 6.94, and 7.56 nmol/L, respectively.
  
  
  CONCLUSIONS
  The Cortisol II assay had good precision over the entire measuring range and had excellent agreement with LC-MS/MS. This test was found suitable for routine diagnostic application and will be valuable for the diagnosis of adrenocortical diseases.
authors.affiliation: Institute of Laboratory Medicine, Hospital of the University of Munich (LMU), Marchioninistr. 15, 81377 Munich.
authors.forename: Michael
authors.initials: M
authors.lastname: Vogeser
authors.affiliation: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Hospital Leipzig, Leipzig.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kratzsch
authors.affiliation: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Hospital Leipzig, Leipzig.
authors.forename: Yoon
authors.initials: Y
authors.lastname: Ju Bae
authors.affiliation: Institute of Laboratory Medicine, Hospital of the University of Munich (LMU), Munich.
authors.forename: Mathias
authors.initials: M
authors.lastname: Bruegel
authors.affiliation: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Hospital Leipzig, Leipzig.
authors.forename: Uta
authors.initials: U
authors.lastname: Ceglarek
authors.affiliation: University Hospital Ghent, Klinische Biologie, Ghent.
authors.forename: Tom
authors.initials: T
authors.lastname: Fiers
authors.affiliation: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Hospital Leipzig, Leipzig.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gaudl
authors.affiliation: Roche Diagnostics GmbH, Penzberg.
authors.forename: Hedwig
authors.initials: H
authors.lastname: Kurka
authors.affiliation: Limbach Laboratory, Medical Care Center, Heidelberg.
authors.forename: Christoph
authors.initials: C
authors.lastname: Milczynski
authors.affiliation: Roche Diagnostics GmbH, Mannheim.
authors.forename: Cristina
authors.initials: C
authors.lastname: Prat Knoll
authors.affiliation: Institute of Laboratory Medicine, Hospital of the University of Munich (LMU), Munich.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Suhr
authors.affiliation: Institute of Laboratory Medicine, Hospital of the University of Munich (LMU), Munich.
authors.forename: Daniel
authors.initials: D
authors.lastname: Teupser
authors.affiliation: Limbach Laboratory, Medical Care Center, Heidelberg.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Zahn
authors.affiliation: Division of Endocrinology, Metabolism and Lipid Research, Washington University, St Louis, MO.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Ostlund
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D003429:Cross Reactions; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis* / Q000097:blood / Q000276:immunology; D057230:Limit of Detection; D012016:Reference Values; D012463:Saliva / Q000737:chemistry
chemical_list: D006854:Hydrocortisone
keywords: assay; cortisol; immunoassay; method comparison; performance evaluation