title: Agreement of seven 25-hydroxy vitamin D₃ immunoassays and three high performance liquid chromatography methods with liquid chromatography tandem mass spectrometry.
abstract: BACKGROUND
  Several recent studies have shown some discrepancies between 25-hydroxyvitamin D [25(OH)D] assay methods, despite some improvement in the past few years. The accuracy of 25(OH)D assay methods is still a real challenge for clinical laboratories. The aim of this study was to assess the agreement between a large panel of routine assays and a two-dimensional liquid chromatography/tandem mass spectrometry (2D LC-MS/MS) method, selected as the reference method.
  
  
  METHODS
  Forty-nine human plasma samples with only endogenous 25(OH)D₃ were analyzed with 11 different methods, especially with three LC-UV methods that differed in the extraction step. Seven routine immunoassays were also tested: two manual (RIA and EIA from IDS) and five fully-automated methods. The results of the 25(OH)D₃ assays were compared with those of the 2D LC-MS/MS method using weighted Deming regression analysis, Bland-Altman plots and concordance correlation coefficient (CCC). The ability of these methods to properly classify patients was evaluated by sorting results depending on vitamin D status.
  
  
  RESULTS
  The CCC was >0.90 for the three LC-UV methods and for most of the automated IA, meaning substantial agreement with 2D LC-MS/MS results. The ability to properly classify patients according to their vitamin D status was overall satisfactory for most of the methods tested (concordance >90%).
  
  
  CONCLUSIONS
  The immunoassays available on Liaison, Isys, Architect and Elecsys, together with our in-house LC-UV method preceded by an SLE step met the minimum requirements for the assessment of vitamin D status in clinical laboratories.
authors.forename: Damien
authors.initials: D
authors.lastname: Denimal
authors.forename: Véronique
authors.initials: V
authors.lastname: Ducros
authors.forename: Thierry
authors.initials: T
authors.lastname: Dupré
authors.forename: Brigitte
authors.initials: B
authors.lastname: Dousset
authors.forename: Cécile
authors.initials: C
authors.lastname: Meunier
authors.forename: Serge
authors.initials: S
authors.lastname: Aho
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Guilland
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lemaire-Ewing
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007118:Immunoassay; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000276:immunology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D