title: Performance evaluation of four 25-hydroxyvitamin D assays to measure 25-hydroxyvitamin D2.
abstract: OBJECTIVE
  The ability of current immunoassays to accurately measure equimolar amounts of 25(OH)D2 and 25(OH)D3 has been recently questioned. This study determined serum 25(OH)D2, 25(OH)D3 and total serum 25(OH)D concentrations in healthy vitamin D2-supplemented subjects by isotope dilution liquid chromatography mass spectrometry (ID-LC-MS/MS); and, evaluated the ability of the Siemens, DiaSorin, Roche, and Abbott Vitamin D Total assays to monitor total serum 25(OH)D concentrations compared to an ID-LC-MS/MS method traceable to the National Institute of Standards and Technology (NIST), and that has achieved certification from the Centers for Disease Control and Prevention (CDC) Vitamin D Standardization Certification Program (VDSCP).
  
  
  METHODS
  Twenty (20) healthy adults, with no history of prior vitamin D supplementation were administered oral vitamin D2 (2400IU/day for 6months). Serum samples (140) from baseline and monthly blood draws were tested.
  
  
  RESULTS
  After one month, the mean serum 25(OH)D2 concentrations rose from 0.8 to 43.6nmol/L, whereas 25(OH)D3 concentrations declined from 84.0 to 63.4nmol/L; total serum 25(OH)D concentrations rose from 86.6 to 107.0nmol/L. The overall mean bias to ID-LC-MS/MS was -7.1% for the Siemens ADVIA Centaur assay, -15.3% for the DiaSorin LIAISON assay; -8.4% for the Roche ELECSYS assay and -16.3% for the Abbott ARCHITECT assay. Correlation coefficients (r) were 0.94, 0.79, 0.74, and 0.73; the mean bias for baseline [25(OH) D3-containing] versus six-month [25(OH)D2- and 25(OH)D3-containing] samples was -13.4% and -5.7%; -3.5% and 20.3%, 9.6% and -12.1%, and 0.2% and -17.8%, respectively.
  
  
  CONCLUSIONS
  The bias results obtained for the Siemens ADVIA Centaur assay and Roche ELECSYS assay were slightly lower than those for the DiaSorin LIAISON assay and the Abbott ARCHITECT assay, but all 25(OH)D assays demonstrated acceptable performance.
authors.affiliation: Siemens Healthcare Diagnostics Inc., 511 Benedict Ave, Tarrytown, NY 10591, USA. Electronic address: james.freeman@siemens.com.
authors.forename: James
authors.initials: J
authors.lastname: Freeman
authors.affiliation: Siemens Healthcare Diagnostics Inc., 511 Benedict Ave, Tarrytown, NY 10591, USA. Electronic address: kimberly.s.wilson@siemens.com.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Wilson
authors.affiliation: Siemens Healthcare Diagnostics Inc., 511 Benedict Ave, Tarrytown, NY 10591, USA. Electronic address: ryan.spears@siemens.com.
authors.forename: Ryan
authors.initials: R
authors.lastname: Spears
authors.affiliation: Siemens Healthcare Diagnostics Inc., 511 Benedict Ave, Tarrytown, NY 10591, USA. Electronic address: victoria.shalhoub@siemens.com.
authors.forename: Victoria
authors.initials: V
authors.lastname: Shalhoub
authors.affiliation: Siemens Healthcare Diagnostics Inc., 511 Benedict Ave, Tarrytown, NY 10591, USA. Electronic address: paul.sibley@siemens.com.
authors.forename: Paul
authors.initials: P
authors.lastname: Sibley
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood* / Q000737:chemistry*; D000328:Adult; D000368:Aged; D001681:Biological Assay / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry; D055815:Young Adult
chemical_list: D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; C104450:25-hydroxyvitamin D
keywords: 25 Hydroxyvitamin D; 25(OH)D; 25(OH)D(2); 25(OH)D(3); ID-LC-MS/MS; VDSCP; Vitamin D; Vitamin D total assay