title: Lack of transferability between different immunoassays and LC-MS/MS for total 25-hydroxyvitamin D measurement and disagreement defining deficiency.
abstract: BACKGROUND
  Over the last few years, it has become much more common to measure concentrations of vitamin D, as its deficiency has been associated with an increasing number of health problems. Recently, a number of new immunoassays for measurement of total 25-hydroxyvitamin D (25OH-D) concentration have been released but their results may not be transferable.
  
  
  METHODS
  Our main objective was to compare results from the Cobas(®) e411 (Roche Diagnostics), Advia Centaur(®) (Siemens), Architect (Abbott), IDS-iSYS (Vitro S.A.), and Liaison(®) (Diasorin) immunoassay systems with each other and with liquid chromatography-tandem mass spectrometry (LC-MS/MS). We obtained 184 routine serum samples, covering the whole measuring range, for these methods.
  
  
  RESULTS
  Kappa values above 0.8 were considered to indicate excellent agreement. With a cut-off of 50 nmol/L Architect and Cobas were the only immunoassay methods able to identify patients with deficiencies consistent with the findings of the reference method LC-MS/MS. On the other hand, using a cut-off of 37.5 nmol/L for Liaison and 75 nmol/L for IDS-iSYS, while maintaining the value of 50 nmol/L for the LC-MS/MS method, kappa values of 0.80 and 0.83 respectively were obtained.
  
  
  CONCLUSIONS
  Choosing the best method for each laboratory is challenging due to methodological differences between them and 50 nmol/L cannot be considered as a general cut-off for defining hypovitaminosis.
authors.affiliation: Clinical Analysis Laboratory, Galdakao-Usansolo Hospital, Galdakao, Bizkaia, Spain. iratxe.ajuriamorentin@osakidetza.net
authors.forename: Iratxe
authors.initials: I
authors.lastname: Ajuria-Morentin
authors.forename: Carmen
authors.initials: C
authors.lastname: Mar-Medina
authors.forename: Edurne
authors.initials: E
authors.lastname: Bereciartua-Urbieta
authors.forename: Fernando
authors.initials: F
authors.lastname: Izquierdo-Quirce
authors.forename: Carmen
authors.initials: C
authors.lastname: Valladares-Gómez
authors.forename: Elia
authors.initials: E
authors.lastname: Crespo-Picot
authors.forename: Torrres
authors.initials: T
authors.lastname: Jaume
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D