title: Method evaluation study of a new generation of vitamin D assays.
abstract: BACKGROUND
  Recently several diagnostic manufacturers have launched new 25-hydroxy-vitamin D (25[OH]D) assays, which are aligned to the National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM) (NIST, Gaithersburg, Maryland). The aim of this study was to compare the performance of one liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, one enzyme linked immunosorbent assay (ELISA), and one recalibrated and previous version of a chemiluminescence immunoassay (CLIA).
  
  
  METHODS
  Serum-aliquots of 198 patient samples from routine 25(OH)D analysis were measured by the ClinMass® LC-MS/MS Complete Kit (RECIPE Chemicals+Instruments GmbH, Munich, Germany), the ORGENTEC 25(OH)D3/D2 ELISA (ORGENTEC Diagnostika GmbH, Mainz, Germany), the recalibrated Immunodiagnostic Systems (IDS)-iSYS 25(OH)DS and the previous used IDS-iSYS 25(OH)D CLIA (Immunodiagnostic Systems Ltd, Boldon, United Kingdom). Bland-Altman and Deming regression analyses were calculated for methods comparison of all tested 25(OH)D assays. The LC-MS/MS method was defined as the reference method. Within-run and between-run precision measurements were performed for all methods with three different concentration levels.
  
  
  RESULTS
  Compared to the LC-MS/MS method, the new IDS-iSYS 25(OH)DS and ORGENTEC 25(OH)D3/D2 assay demonstrated mean relative biases of 16.3% and 17.8%. The IDS-iSYS 25(OH)D assay showed the lowest mean bias of 1.5%. Deming regression analyses of the recalibrated IDS-iSYS 25(OH)DS and the ORGENTEC 25(OH)D3/D2 assay showed proportional differences, when compared to the reference method. All assays showed a within-run and between-run imprecision of ≤20% at each of the evaluated concentration levels.
  
  
  CONCLUSIONS
  The evaluated standardized immunoassays and LC-MS/MS are useful methods for measuring 25(OH)D serum-levels in clinical laboratories.
authors.affiliation: Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Enko
authors.affiliation: Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria.
authors.forename: Gernot
authors.initials: G
authors.lastname: Kriegshäuser
authors.affiliation: Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Stolba
authors.affiliation: Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria.
authors.forename: Elfriede
authors.initials: E
authors.lastname: Worf
authors.affiliation: Institute of Laboratory Medicine, General Hospital Steyr, Steyr, Austria.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Halwachs-Baumann
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods* / Q000592:standards*; D012015:Reference Standards; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: immunoassays; liquid chromatography-tandem mass spectrometry; quality improvement; reference standards; vitamin D