title: Variation in clinical vitamin D status by DiaSorin Liaison and LC-MS/MS in the presence of elevated 25-OH vitamin D2.
abstract: BACKGROUND
  We compared total 25-OH vitamin D status measured by DiaSorin Liaison and tandem mass spectrometry (LC-MS/MS) among patients with high and low 25-OH vitamin D(2).
  
  
  METHODS
  Total 25-OH vitamin D was measured in plasma containing high (>25 nmol/l or >50%, n=26) and low (<2.5 nmol/l, n=29) 25-OH vitamin D(2) using DiaSorin Liaison and an LC-MS/MS method using NIST 972-verified calibrators. Samples were classified as vitamin D adequate (total 25-OH vitamin D ≥50 nmol/l), and inadequate or deficient (<50 nmol/l) by each method. Deming and multiple linear regression were used to compare methods.
  
  
  RESULTS
  Samples were significantly more likely to be classified as inadequate or deficient by DiaSorin Liaison (36%) vs LC-MS/MS (9%). This increased in the presence of high 25-OH vitamin D2 (42% vs 0%). Total 25-OH vitamin D by DiaSorin Liaison was 26.0 nmol/l lower than LC-MS/MS, which increased to 34.1 nmol/l among samples with high 25-OH vitamin D(2). This was attributed to lower recovery of 25-OH vitamin D(2) (proportional bias=0.64 nmol/l) by DiaSorin Liaison, independent of D(3) (proportional bias=0.86 nmol/l).
  
  
  CONCLUSIONS
  Patients were more likely to be classified as vitamin D inadequate or deficient by DiaSorin Liaison compared to an LC-MS/MS method, which was in part due to the presence of 25-OH vitamin D(2).
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Lawrence
authors.initials: L
authors.lastname: de Koning
authors.forename: M Rabie
authors.initials: MR
authors.lastname: Al-Turkmani
authors.forename: Anders H
authors.initials: AH
authors.lastname: Berg
authors.forename: Aida
authors.initials: A
authors.lastname: Shkreta
authors.forename: Terence
authors.initials: T
authors.lastname: Law
authors.forename: Mark D
authors.initials: MD
authors.lastname: Kellogg
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D002853:Chromatography, Liquid / Q000592:standards* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards* / Q000706:statistics & numerical data; D007223:Infant; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000592:standards* / Q000706:statistics & numerical data; D014807:Vitamin D / Q000097:blood*
chemical_list: D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2