title: Multicenter comparison of cortisol as measured by different methods in samples of patients with septic shock.
abstract: OBJECTIVE
  To compare inter-laboratory and inter-assay measurements of total cortisol in patients with septic shock and to evaluate current recommendations for diagnosis of corticosteroid insufficiency in septic shock.
  
  
  METHODS
  In the multinational CORTICUS study duplicate serum samples were taken before and after corticotropin stimulation tests in patients with septic shock. Serum cortisol was measured in paired samples, one being measured by the chemical laboratory of each participating site and the other by a central laboratory using an electrochemiluminescence immunoassay. Cortisol levels measured by tandem mass spectrometry were used as a 'gold standard' reference method in a subset of samples.
  
  
  RESULTS
  A total of 425 corticotropin tests (850 cortisol samples) were available for comparison of local and central laboratory measurements. The concordance correlation coefficient between central laboratory immunoassay and local hospital assays was 0.98 (CI 0.97-0.99) when the immunoassay of one manufacturer was used and 0.60 (CI 0.54-0.65) when immunoassays of different manufacturers were used. The comparison with the reference method of mass spectrometry showed concordance correlation coefficients ranging from 0.43 to 0.97 depending on the assay under study. Diagnosis of corticosteroid insufficiency was diverging due to inter-assay variations in up to 27% of cases.
  
  
  CONCLUSIONS
  In samples taken from patients in septic shock, there was a high inter-assay variation of total serum cortisol. Comparisons with a reference method revealed both over- and underestimations of true cortisol levels. These inter-assay variations in samples of patients with septic shock complicate the diagnosis of corticosteroid insufficiency.
authors.affiliation: Klinik für Anästhesiologie, Klinikum der Ludwig-Maximilians-Universität München, 81366 Munich, Germany. Josef.Briegel@med.uni-muenchen.de
authors.forename: Josef
authors.initials: J
authors.lastname: Briegel
authors.forename: Charles L
authors.initials: CL
authors.lastname: Sprung
authors.forename: Djillali
authors.initials: D
authors.lastname: Annane
authors.forename: Mervyn
authors.initials: M
authors.lastname: Singer
authors.forename: Didier
authors.initials: D
authors.lastname: Keh
authors.forename: Rui
authors.initials: R
authors.lastname: Moreno
authors.forename: Patrick
authors.initials: P
authors.lastname: Möhnle
authors.forename: Yoram
authors.initials: Y
authors.lastname: Weiss
authors.forename: Alexander
authors.initials: A
authors.lastname: Avidan
authors.forename: Frank M
authors.initials: FM
authors.lastname: Brunkhorst
authors.forename: Fritz
authors.initials: F
authors.lastname: Fiedler
authors.forename: Michael
authors.initials: M
authors.lastname: Vogeser
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism; D019411:Clinical Laboratory Techniques / Q000295:instrumentation* / Q000706:statistics & numerical data*; D005938:Glucocorticoids; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007118:Immunoassay / Q000379:methods; D012772:Shock, Septic / Q000097:blood*
chemical_list: D005938:Glucocorticoids; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone