title: Evaluation of the analytical performance of Unicel DXI 800 for the Total 25 (OH) Vitamin D measurements.
abstract: OBJECTIVE
  We assessed the analytical performance of newly developed Access 25(OH) Vitamin D Total assay with Beckman Coulter Unicel DXI 800 and evaluated the agreement between a reference method liquid chromatography/tandem mass spectrometry (LC-MS/MS) and a chemiluminescence method (LIAISON, DiaSorin).
  
  
  METHODS
  160 serum samples were included. Deming Regression analysis and Bland-Altman plots were used. The concordance correlation coefficient (CCC) was used to assess the degree of agreement between assays and the reference method.
  
  
  RESULTS
  The CV% values of Unicel DXI 800 for within-run, between-run and between-day were lower than 6%. When compared to LC-MS/MS, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9444 (intercept -0.089, slope 0.951), with an average bias of -2.9%, and the LIAISON 25(OH) Vitamin D Total assay an R value of 0.9405 (intercept -0605, slope 0.924), with an average bias of -13.6%. In comparison with the LIAISON 25(OH) Vitamin D Total assay, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9498 (intercept 0.528, slope 1.029), with an average bias of 1.2%. The agreement with the LC-MS/MS method, based on values of the CCC, was moderate for the Unicel DXI 800 and LIAISON method (0.95, 0.94 respectively).
  
  
  CONCLUSIONS
  The new, automated Access 25(OH) Vitamin D Total assay showed an acceptable correlation with LC-MS/MS and LIAISON. Both methods moderately achieved to classify the patients according to their vitamin D status. However, we need further standardization of vitamin D assays to enhance the accuracy and comparability.
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey. Electronic address: nersoyozcan@gmail.com.
authors.forename: Nurgul
authors.initials: N
authors.lastname: Ozcan
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Fatma
authors.initials: F
authors.lastname: Ucar
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Abdullah Ercan
authors.initials: AE
authors.lastname: Arzuhal
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Erdem
authors.initials: E
authors.lastname: Bulut
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Alpaslan
authors.initials: A
authors.lastname: Ozturk
authors.affiliation: Hacettepe University, Faculty of Medicine, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Mine
authors.initials: M
authors.lastname: Taslipinar Yavuz
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Ismail
authors.initials: I
authors.lastname: Temel
authors.affiliation: Diskapi Yildirim Beyazit Training and Research Hospital, Department of Clinical Biochemistry, Ankara, Turkey; Hacettepe University, Faculty of Medicine, Department of Clinical Biochemistry, Ankara, Turkey.
authors.forename: Gonul
authors.initials: G
authors.lastname: Erden
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-OH Vitamin D; DiaSorin LIAISON; Immunoassay; LC–MS/MS; Method comparison; Unicel DXI 800