title: Comparison of automated methods for measurement of 25-hydroxyvitamin D.
abstract: BACKGROUND
  The objective of the study was to compare the analytical performance of three automated immunoassays for the determination of serum 25-hydroxyvitamin D.
  
  
  METHODS
  Quantitative determination of serum 25(OH)D were performed by "Vitamin D total" (n = 131) and "Vitamin D3(25-OH)" (n = 77) assays (Roche Diagnostics) on a Cobas e411 and by "25-OH Vitamin D" (n = 131) assay (Abbott Laboratories) on an Architect. The inter-assay precision was calculated and methods were compared by the Passing Bablok regression and Bland-Altman analysis.
  
  
  RESULTS
  The "Vitamin D total" demonstrated stronger correlation (r = 0.863) and better agreement (bias = -7.89 nmol/L) with the "25-OH Vitamin D" than with the "Vitamin D3(25-OH)" (r = 0.716; bias = +18.6 nmol/L). The inter-assay precision (% CV) for the "Vitamin D total" and "25-OH Vitamin D" assays, were respectively 3.47 to 6.14 and 4.27 to 8.56.
  
  
  CONCLUSIONS
  The results of this study demonstrate that Abbott "25-OH Vitamin D" and Roche "Vitamin D total" are rapid and precise methods for 25(OH)D serum measurement over a wide reportable range on automated immunoassay platforms. The Abbott assay exhibited better correlation and agreement with the new Roche assay than the "Vitamin D3(25-OH)" Roche assay. Between method differences observed in this study still indicates the need for standardization of 25(OH)D assays.
authors.affiliation: Centro Hospitalar do Porto, Hospital de Santo António, Serviço de Química Clínica, Porto, Portugal. pcmcosta@live.com.pt
authors.forename: Paula
authors.initials: P
authors.lastname: Martins-Costa
authors.forename: Helena
authors.initials: H
authors.lastname: Martins
authors.forename: Fernanda
authors.initials: F
authors.lastname: Bravo
authors.forename: Madalena
authors.initials: M
authors.lastname: Cruz
authors.forename: Júlia
authors.initials: J
authors.lastname: Reis
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Oliveira
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001331:Automation; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D