title: Total 25-hydroxyvitamin D determination by an entry level triple quadrupole instrument: comparison between two commercial kits.
abstract: OBJECTIVE
  25-hydroxyvitamin D2/D3 (25-OHD2/D3) determination is a reliable biomarker for vitamin D status. Liquid chromatography-tandem mass spectrometry was recently proposed as a reference method for vitamin D status evaluation. The aim of this work is to compare two commercial kits (Chromsystems and PerkinElmer) for 25-OHD2/D3 determination by our entry level LC-MS/MS.
  
  
  METHODS
  Chromsystems kit adds an online trap column to an HPLC column and provides atmospheric pressure chemical ionization, isotopically labeled internal standard, and 4 calibrator points. PerkinElmer kit uses a solvent extraction and protein precipitation method. This kit can be used with or without derivatization with, respectively, electrospray and atmospheric pressure chemical ionization. For each analyte, there are isotopically labeled internal standards and 7 deuterated calibrator points.
  
  
  RESULTS
  Performance characteristics are acceptable for both methods. Mean bias between methods calculated on 70 samples was 1.9 ng/mL. Linear regression analysis gave an R (2) of 0.94. 25-OHD2 is detectable only with PerkinElmer kit in derivatized assay option.
  
  
  CONCLUSIONS
  Both methods are suitable for routine. Chromsystems kit minimizes manual sample preparation, requiring only protein precipitation, but, with our system, 25-OHD2 is not detectable. PerkinElmer kit without derivatization does not guarantee acceptable performance with our LC-MS/MS system, as sample is not purified online. Derivatization provides sufficient sensitivity for 25-OHD2 detection.
authors.affiliation: Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo A. Gemelli 8, 00168 Rome, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Gervasoni
authors.forename: Andrea
authors.initials: A
authors.lastname: Cocci
authors.forename: Cecilia
authors.initials: C
authors.lastname: Zuppi
authors.forename: Silvia
authors.initials: S
authors.lastname: Persichilli
mesh_terms: D000293:Adolescent; D000328:Adult; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000302:isolation & purification*
chemical_list: D011933:Reagent Kits, Diagnostic; D014807:Vitamin D; C104450:25-hydroxyvitamin D
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