title: 3-epi-25 hydroxyvitamin D concentrations are not correlated with age in a cohort of infants and adults.
abstract: BACKGROUND
  The implementation of mass spectrometry to measure serum 25-hydroxyvitamin D [25(OH)D] concentrations has led to concerns regarding the measurement and reporting of the C3-epimer of 25-hydroxyvitamin D(3) [3-epi-25(OH)D(3)], for which there is a near-total lack of data regarding its clinical significance.
  
  
  METHODS
  We developed a chromatographic method to resolve (>90%) 3-epi-25(OH)D(3) from 25(OH)D(3) using a pentafluorophenyl propyl chromatographic column. Using LC-MS/MS, we determined the serum concentrations of 25(OH)D(3) and 3-epi-25(OH)D(3) in 626 patients aged 3 days to 94 years undergoing routine vitamin D testing.
  
  
  RESULTS
  Comparison between DiaSorin RIA and the new LC-MS/MS method for total 25(OH)D had acceptable agreement. Our data indicate an increase in 25(OH)D(3) rather than a reduction in epimer concentration. An average of 3.3 ng/ml of 3-epi-25(OH)D(3) was detected in adolescents and adults. Inclusion of 3-epi-25(OH)D(3) in the total 25(OH)D(3) concentration resulted in 9% (<1 year) and 3% (1 to 94 years) potential misclassification of patients as vitamin D sufficient.
  
  
  CONCLUSIONS
  The new LC-MS/MS method is capable of chromatographically separating 25(OH)D(3) and 3-epi-25(OH)D(3). It was used to confirm that the contribution of 3-epi-25OHD(3) to total 25OHD(3) concentrations decreases with age in infants and is detectable in adults.
authors: Department of Laboratory Medicine, University of Washington, Seattle, WA 98195, United States.
authors: Frederick G
authors: FG
authors: Strathmann
authors: Katerina
authors: K
authors: Sadilkova
authors: Thomas J
authors: TJ
authors: Laha
authors: Susan E
authors: SE
authors: LeSourd
authors: Joshua A
authors: JA
authors: Bornhorst
authors: Andrew N
authors: AN
authors: Hoofnagle
authors: Rhona
authors: R
authors: Jack
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002853:Chromatography, Liquid; D015331:Cohort Studies; D006801:Humans; D007223:Infant; D008875:Middle Aged; D011863:Radioimmunoassay; D053719:Tandem Mass Spectrometry; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D