title: Serum Cortisol: An Up-To-Date Assessment of Routine Assay Performance.
abstract: Accurate serum cortisol quantification is required for the correct diagnosis and management of adrenal pathologies. Presently, most laboratories use immunoassay to measure serum cortisol with proficiency schemes demonstrating a wide dispersion of results. Here, we investigate the effects of sex, matrix, and antibody specificity on serum cortisol quantification in 6 routine assays.
  
  
  
  Surplus serum was obtained before disposal and the following cohorts were created: males, nonpregnant females, pregnant patients, and patients prescribed either metyrapone or prednisolone. Samples were anonymized and distributed to collaborating laboratories for cortisol analysis by 6 routine assays. Cortisol was also measured in all samples using an LC-MS/MS candidate reference measurement procedure (cRMP); cortisol-binding globulin (CBG) was measured in the nonpregnant and pregnant female cohorts.
  
  
  
  Considerable inter- and intraassay variation was observed across the male and nonpregnant female cohorts relative to the cRMP. Four immunoassays underrecovered cortisol in the pregnancy cohort, and CBG was found to be significantly higher in this cohort than in the nonpregnant females. In the metyrapone and prednisolone cohorts, all immunoassays overestimated cortisol. The first generation Roche E170 and Siemens Centaur XP were particularly prone to overestimation. In all cohorts the routine LC-MS/MS assay aligned extremely well with the cRMP.
  
  
  
  Despite the clinical importance of serum cortisol, the performance of routine immunoassays remains highly variable. Accurate quantification is compromised by both matrix effects and antibody specificity. Underpinning this study with a cRMP has highlighted the deficiencies in standardization across routine cortisol immunoassays.
authors.affiliation: University Hospital South Manchester, Manchester, UK; james.hawley@uhsm.nhs.uk.
authors.forename: James M
authors.initials: JM
authors.lastname: Hawley
authors.affiliation: University Hospital South Manchester, Manchester, UK; Manchester Academic Health Science Centre, Manchester, UK;
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Owen
authors.affiliation: University Hospital South Manchester, Manchester, UK;
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lockhart
authors.affiliation: The Christie Pathology Partnership, The Christie NHS Foundation Trust, Manchester, UK;
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Monaghan
authors.affiliation: Southampton Hospital, Southampton, UK;
authors.forename: Annie
authors.initials: A
authors.lastname: Armston
authors.affiliation: Aintree Hospital, Liverpool, UK;
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Chadwick
authors.affiliation: Aintree Hospital, Liverpool, UK;
authors.forename: Heather
authors.initials: H
authors.lastname: Wilshaw
authors.affiliation: St. Georges' University Hospital, London, UK;
authors.forename: Maisa
authors.initials: M
authors.lastname: Freire
authors.affiliation: Croydon University Hospital, London, UK.
authors.forename: Leslie
authors.initials: L
authors.lastname: Perry
authors.affiliation: University Hospital South Manchester, Manchester, UK; Manchester Academic Health Science Centre, Manchester, UK;
authors.forename: Brian G
authors.initials: BG
authors.lastname: Keevil
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy
chemical_list: D006854:Hydrocortisone