title: Evaluation of automated immunoassays for 25(OH)-vitamin D determination in different critical populations before and after standardization of the assays.
abstract: BACKGROUND
  Standardization of immunoassays for 25(OH)-vitamin D determination is a major problem in clinical practice. A worldwide standardization program has started to address this and will reduce the bias observed between immunoassays. We aimed to calibrate 5 immunoassays on a LC-MS/MS traceable to the SRM 2972 and the ID-LC-MS/MS 25(OH)D Reference Method Procedure to see if the re-standardization would be efficient in a population of 3rd trimester pregnant women (PW), hemodialysis (HD) and osteoporosis (OP) patient.
  
  
  METHODS
  184 serum samples (25(OH)D: 8.4-87 ng/ml) were selected to calibrate the immunoassays (Abbott-Architect, Roche-Elecsys, DiaSorin-Liaison, Siemens-Centaur and IDS-iSYS). Chromsystems MassChrom method was used as the referenced. Serum obtained in 34 PW, 25 HD and 34 OP patients were used as comparatives.
  
  
  RESULTS
  After adjusting to LC-MS/MS, immunoassays had regression slopes nearly identical to 1.0 with intercepts <0.5 ng/ml. However, in special populations, a systematic bias was still observed, except for iSYS.
  
  
  CONCLUSIONS
  Re-standardization of 25(OH)D immunoassay will globally improve the differences. However, patients with a different serum matrix will still present significantly different results when they will be run with different methods. For those patients, the LC-MS/MS method seems to be the method of choice, even if some immunoassays are less influenced than others.
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium. Electronic address: Etienne.cavalier@chu.ulg.ac.be.
authors: Etienne
authors: E
authors: Cavalier
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Pierre
authors: P
authors: Lukas
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Yannick
authors: Y
authors: Crine
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Stéphanie
authors: S
authors: Peeters
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Agnès
authors: A
authors: Carlisi
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Caroline
authors: C
authors: Le Goff
authors: Department of Clinical Chemistry, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Romy
authors: R
authors: Gadisseur
authors: Nephrology Dialysis and Hypertension, University of Liege, CHU Sart-Tilman, Liege, Belgium.
authors: Pierre
authors: P
authors: Delanaye
authors: Laboratoire d'Explorations Fonctionnelles, Hôpital Necker-Enfants Maladies, Paris, France.
authors: Jean-Claude
authors: JC
authors: Souberbielle
mesh_terms: D000328:Adult; D001331:Automation; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D007118:Immunoassay / Q000379:methods; D013058:Mass Spectrometry; D010024:Osteoporosis / Q000097:blood; D011247:Pregnancy; D012015:Reference Standards; D006435:Renal Dialysis; D015203:Reproducibility of Results; D014809:Vitamin D-Binding Protein / Q000097:blood
chemical_list: D006887:Hydroxycholecalciferols; D014809:Vitamin D-Binding Protein
keywords: Standardization; Uremia; Vitamin D; Vitamin D–binding protein