TY - JOUR
T1 - Free 25-hydroxyvitamin D
T2 - Impact of vitamin D binding protein assays on racial-genotypic associations
AU - Osteoporotic Fractures in Men (MrOS) Research Group
AU - Nielson, Carrie M.
AU - Jones, Kerry S.
AU - Chun, Rene F.
AU - Jacobs, Jon M.
AU - Wang, Ying
AU - Hewison, Martin
AU - Adams, John S.
AU - Swanson, Christine M.
AU - Lee, Christine G.
AU - Vanderschueren, Dirk
AU - Pauwels, Steven
AU - Prentice, Ann
AU - Smith, Richard D.
AU - Shi, Tujin
AU - Gao, Yuqian
AU - Schepmoes, Athena A.
AU - Zmuda, Joseph M.
AU - Lapidus, Jodi
AU - Cauley, Jane A.
AU - Bouillon, Roger
AU - Schoenmakers, Inez
AU - Orwoll, Eric S.
N1 - Publisher Copyright:
Copyright © 2016 by the Endocrine Society
PY - 2016/5
Y1 - 2016/5
N2 - Context: Total 25-hydroxyvitamin D (25OHD) is a marker of vitamin D status and is lower in African Americans than in whites. Whether this difference holds for free 25OHOD (f25OHD) is unclear, considering reported genetic-racial differences in vitaminDbinding protein (DBP) used to calculate f25OHD. Objectives: Our objective was to assess racial-geographic differences in f25OHD and to understand inconsistencies in racial associations with DBP and calculated f25OHD. Design: This study used a cross-sectional design. Setting: The general community in the United States, United Kingdom, and The Gambia were included in this study. Participants: Men in Osteoporotic Fractures in Men and Medical Research Council studies (N = 1057) were included. Exposures: Total 25OHD concentration, race, and DBP (GC) genotype exposures were included. Outcome Measures: Directly measured f25OHD, DBP assessed by proteomics, monoclonal and polyclonal immunoassays, and calculated f25OHD were the outcome measures. Results: Total 25OHD correlated strongly with directly measured f25OHD (Spearman r = 0.84). Measured by monoclonal assay, mean DBP in African-ancestry subjects was approximately 50% lower than in whites, whereas DBP measured by polyclonal DBP antibodies or proteomic methods was not lower in African-ancestry. Calculated f25OHD (using polyclonal DBP assays) correlated strongly with directly measured f25OHD (r = 0.80-0.83). Free 25OHD, measured or calculated from polyclonal DBP assays, reflected total 25OHD concentration irrespective of race and was lower in African Americans than in US whites. Conclusions: Previously reported racial differences in DBP concentration are likely from monoclonal assay bias, as there was no racial difference in DBP concentration by other methods. This confirms the poor vitamin D status of many African-Americans and the utility of total 25OHD in assessing vitamin D in the general population.
AB - Context: Total 25-hydroxyvitamin D (25OHD) is a marker of vitamin D status and is lower in African Americans than in whites. Whether this difference holds for free 25OHOD (f25OHD) is unclear, considering reported genetic-racial differences in vitaminDbinding protein (DBP) used to calculate f25OHD. Objectives: Our objective was to assess racial-geographic differences in f25OHD and to understand inconsistencies in racial associations with DBP and calculated f25OHD. Design: This study used a cross-sectional design. Setting: The general community in the United States, United Kingdom, and The Gambia were included in this study. Participants: Men in Osteoporotic Fractures in Men and Medical Research Council studies (N = 1057) were included. Exposures: Total 25OHD concentration, race, and DBP (GC) genotype exposures were included. Outcome Measures: Directly measured f25OHD, DBP assessed by proteomics, monoclonal and polyclonal immunoassays, and calculated f25OHD were the outcome measures. Results: Total 25OHD correlated strongly with directly measured f25OHD (Spearman r = 0.84). Measured by monoclonal assay, mean DBP in African-ancestry subjects was approximately 50% lower than in whites, whereas DBP measured by polyclonal DBP antibodies or proteomic methods was not lower in African-ancestry. Calculated f25OHD (using polyclonal DBP assays) correlated strongly with directly measured f25OHD (r = 0.80-0.83). Free 25OHD, measured or calculated from polyclonal DBP assays, reflected total 25OHD concentration irrespective of race and was lower in African Americans than in US whites. Conclusions: Previously reported racial differences in DBP concentration are likely from monoclonal assay bias, as there was no racial difference in DBP concentration by other methods. This confirms the poor vitamin D status of many African-Americans and the utility of total 25OHD in assessing vitamin D in the general population.
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U2 - 10.1210/jc.2016-1104
DO - 10.1210/jc.2016-1104
M3 - Article
C2 - 27007693
AN - SCOPUS:84969822892
SN - 0021-972X
VL - 101
SP - 2226
EP - 2234
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 5
ER -