PLoS ONE (Jan 2021)

Development and analytical validation of a novel bioavailable 25-hydroxyvitamin D assay.

  • Anders H Berg,
  • Mahtab Tavasoli,
  • Agnes S Lo,
  • Sherri-Ann M Burnett-Bowie,
  • Ishir Bhan,
  • S Ananth Karumanchi,
  • Sahir Kalim,
  • Dongsheng Zhang,
  • Sophia Zhao,
  • Ravi I Thadhani

DOI
https://doi.org/10.1371/journal.pone.0254158
Journal volume & issue
Vol. 16, no. 7
p. e0254158

Abstract

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BackgroundBioavailable 25-hydroxyvitamin D (25OHD) may be a better indicator of vitamin D sufficiency than total 25OHD. This report describes a novel assay for measuring serum bioavailable 25OHD.MethodsWe developed an assay for 25OHD % bioavailability based on competitive binding of 25OHD tracer between vitamin D-binding protein (DBP)-coated affinity chromatography beads and serum DBP. Bioavailable 25OHD, total 25OHD, albumin, and DBP protein concentrations were measured in 89 samples from hospitalized patients and 42 healthy controls to determine how the DBP binding assay responds to differences in concentrations of DBP and compares to calculated bioavailable 25OHD values.ResultsDBP binding assay showed a linear relationship between DBP-bound 25OHD tracer recovered from bead supernatant and DBP calibrator concentrations (y = 0.0017x +0.731, R2 = 0.9961, pConclusionsThe DBP-binding assay for bioavailable 25OHD shows expected changes in 25OHD % bioavailability in response to changes in DBP concentrations and concordance with calculated bioavailable 25OHD concentrations.