Role of Assay Type in Determining Free 25-Hydroxyvitamin D Levels in Diverse Populations
- Carrie M. Nielson
- Kerry S. Jones
- Rene F. Chun
- Jon Jacobs
- Ying Wang
- Martin Hewison
- John S. Adams
- Christine M. Swanson
- Christine G. Lee
- Dirk Vanderschueren
- Steven Pauwels
- Ann Prentice
- Richard Smith
- Tujin Shi
- YGYuqian Gao
- Joseph M. Zmuda
- Jodi Lapidus
- Jane A. Cauley
- Roger Bouillon
- Inez Schoenmakers
- Eric Orwoll
- YGYuqian Gao
New England Journal of Medicine · 2016 · Massachusetts Medical Society
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Abstract
To the Editor: It is unclear whether circulating free or bioavailable 25-hydroxyvitamin D is a better marker of vitamin D status than is total 25-hydroxyvitamin D, especially in racially diverse populations. Until recently, the only method to compare the levels was to estimate the level of free or bioavailable 25-hydroxyvitamin D from total 25-hydroxyvitamin D, vitamin D-binding protein (also known as gc-globulin, encoded by the GC gene), and albumin, with or without the GC genotype. Powe et al. reported that levels of vitamin D-binding protein, as measured on a monoclonal enzyme-linked immunosorbent assay (ELISA, R&D Systems), were lower in black . . .