title: Analytical validation of the Roche 25-OH Vitamin D Total assay.
abstract: BACKGROUND
  Vitamin D deficiency is considered a major health issue and therefore there is a need for reliable routine tests for measurement of the vitamin in blood samples. Here we present a validation of the recently released Roche 25-OH Vitamin D Total assay (Vitamin D Total).
  
  
  METHODS
  We analyzed control materials (2 levels) and patient serum pools (3 levels) ranging from 34 to 123 nmol/L 84 times over a period of 21 days, and we analyzed five serum pools in 10 separate runs to verify the limit of quantification. We also analyzed 53 paired samples of serum and Li-heparin plasma. We evaluated the 25-OH Vitamin D Total assay in comparison to our in-house liquid chromatography tandem mass spectrometry (LC-MS/MS) method [194 patient samples without 25-hydroxy vitamin D(2) (25OHD(2)) and 23 patient samples containing 25OHD(2)].
  
  
  RESULTS
  At concentrations of 34 and 56 nmol/L within-run CVs were 4.8% and 1.9% and total CVs were 8.3% and 6.1%. We verified that the limit of quantification was 22.5 nmol/L, as stated by the manufacturer. No significant difference was observed between serum and plasma samples (Li-heparin). Comparison with LC-MS/MS using 194 samples containing 25OHD(3) only (no 25OHD(2)) showed Vitamin D Total nmol/L=1.07×(LC-MS/MS) nmol/L+4.7 nmol/L, whereas comparison of 25OHD(2) using 23 patient samples showed Vitamin D Total nmol/L=0.55×(LC-MS/MS) nmol/L-2.38 nmol/L (Demings regression).
  
  
  CONCLUSIONS
  The Roche Vitamin D Total assay is judged suitable for measurement of 25OHD in serum and Li-heparin plasma. Results for 25OHD(3) are comparable to those obtained by LC-MS/MS, while results for 25OHD(2) are around half of those obtained by LC-MS/MS.
authors.affiliation: Department of Clinical Biochemistry, Aarhus University Hospital, Denmark. cinknu@rm.dk
authors.forename: Cindy Soendersoe
authors.initials: CS
authors.lastname: Knudsen
authors.forename: Ebba
authors.initials: E
authors.lastname: Nexo
authors.forename: Carsten Schriver
authors.initials: CS
authors.lastname: Højskov
authors.forename: Lene
authors.initials: L
authors.lastname: Heickendorff
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D006801:Humans; D012015:Reference Standards; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D