title: Evaluation of Vitamin D Standardization Program protocols for standardizing serum 25-hydroxyvitamin D data: a case study of the program's potential for national nutrition and health surveys.
abstract: BACKGROUND
  The Vitamin D Standardization Program (VDSP) has developed protocols for standardizing procedures of 25-hydroxyvitamin D [25(OH)D] measurement in National Health/Nutrition Surveys to promote 25(OH)D measurements that are accurate and comparable over time, location, and laboratory procedure to improve public health practice.
  
  
  OBJECTIVE
  We applied VDSP protocols to existing ELISA-derived serum 25(OH)D data from the Irish National Adult Nutrition Survey (NANS) as a case-study survey and evaluated their effectiveness by comparison of the protocol-projected estimates with those from a reanalysis of survey serums by using liquid chromatography-tandem mass spectrometry (LC-tandem MS).
  
  
  METHODS
  The VDSP reference system and protocols were applied to ELISA-based serum 25(OH)D data from the representative NANS sample (n = 1118). A reanalysis of 99 stored serums by using standardized LC-tandem MS and resulting regression equations yielded predicted standardized serum 25(OH)D values, which were then compared with LC-tandem MS reanalyzed values for all serums.
  
  
  RESULTS
  Year-round prevalence rates for serum 25(OH)D concentrations <30, <40, and <50 nmol/L were 6.5%, 21.9%, and 40.0%, respectively, via original ELISA measurements and 11.4%, 25.3%, and 43.7%, respectively, when VDSP protocols were applied. Differences in estimates at <30- and <40-nmol/L thresholds, but not at the <50-nmol/L threshold, were significant (P < 0.05). A reanalysis of all serums by using LC-tandem MS confirmed prevalence estimates as 11.2%, 27.2%, and 45.0%, respectively. Prevalences of serum 25(OH)D concentrations >125 nmol/L were 1.2%, 0.3%, and 0.6% by means of ELISA, VDSP protocols, and LC-tandem MS, respectively.
  
  
  CONCLUSIONS
  VDSP protocols hold a major potential for national nutrition and health surveys in terms of the standardization of serum 25(OH)D data.
authors.affiliation: School of Food and Nutritional Sciences, University College Cork, Cork, Ireland. k.cashman@ucc.ie
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Cashman
authors.forename: Mairead
authors.initials: M
authors.lastname: Kiely
authors.forename: Michael
authors.initials: M
authors.lastname: Kinsella
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Durazo-Arvizu
authors.forename: Lu
authors.initials: L
authors.lastname: Tian
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Alice
authors.initials: A
authors.lastname: Lucey
authors.forename: Albert
authors.initials: A
authors.lastname: Flynn
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gibney
authors.forename: Hubert W
authors.initials: HW
authors.lastname: Vesper
authors.forename: Karen W
authors.initials: KW
authors.lastname: Phinney
authors.forename: Paul M
authors.initials: PM
authors.lastname: Coates
authors.forename: Mary F
authors.initials: MF
authors.lastname: Picciano
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Sempos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002853:Chromatography, Liquid / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay; D017408:Guidelines as Topic; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D009749:Nutrition Surveys; D009752:Nutritional Status; D012015:Reference Standards; D012621:Seasons; D053719:Tandem Mass Spectrometry / Q000379:methods; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood* / Q000592:standards*; D014808:Vitamin D Deficiency / Q000517:prevention & control; D055815:Young Adult
chemical_list: D014807:Vitamin D