What question did this study set out to answer?

To directly measure circulating free 25-hydroxyvitamin D [25(OH)D] concentrations and evaluate their relationship to total 25(OH)D across a clinically diverse adult population.

June 27, 2018The Journal of Clinical Endocrinology & MetabolismOpen Access

Determination of Free 25(OH)D Concentrations and Their Relationships to Total 25(OH)D in Multiple Clinical Populations

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To directly measure circulating free 25-hydroxyvitamin D [25(OH)D] concentrations and evaluate their relationship to total 25(OH)D across a clinically diverse adult population.
Cross-sectional analysis of 1,661 adults across seven academic sites, including healthy individuals (n = 279), prediabetic patients (n = 479), outpatients (n = 714), cirrhotic patients (n = 90), pregnant women (n = 20), and nursing home residents (n = 79).
Free 25(OH)D was measured via direct immunoassay, total 25(OH)D by liquid chromatography/tandem mass spectrometry, and vitamin D-binding protein (DBP) by radial immunodiffusion assay alongside DBP haplotype genotyping.
Mixed-effects modeling examined relationships between free and total 25(OH)D, controlling for clinical condition, DBP haplotype, race, sex, BMI, and estimated glomerular filtration rate (eGFR).
Free 25(OH)D averaged 4.7 ± 1.8 pg/mL in healthy adults and 4.3 ± 1.9 pg/mL in outpatients, but was significantly higher in patients with cirrhosis (7.1 ± 3.0 pg/mL; P < 0.0033) and nursing home residents (7.9 ± 2.1 pg/mL; P < 0.0033).
Free 25(OH)D concentrations differed significantly between Black and white participants (P < 0.0033) and across DBP haplotypes (P < 0.0001).
Mixed-effects modeling demonstrated that underlying clinical conditions (cirrhosis > nursing home residents > prediabetes > outpatients > pregnant women) and BMI significantly altered the relationship between total and free 25(OH)D, whereas sex, race, eGFR, and DBP haplotype did not.

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Implication

Cross-sectional analysis reveals clinical conditions and body mass index alter free-to-total vitamin D relationships in diverse patient cohorts, highlighting potential limits of standard testing.

Cite This Study

Schwartz et al. (2018) studied this question.

synapsesocial.com/papers/6aa7f15db05f134000da0f22 https://doi.org/10.1210/jc.2018-00295

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Implication

Cross-sectional analysis reveals clinical conditions and body mass index alter free-to-total vitamin D relationships in diverse patient cohorts, highlighting potential limits of standard testing.

Determination of Free 25(OH)D Concentrations and Their Relationships to Total 25(OH)D in Multiple Clinical Populations

Key Points

Discussion

Implication

Cite This Study

Determination of Free 25(OH)D Concentrations and Their Relationships to Total 25(OH)D in Multiple Clinical Populations

Key Points

Discussion

Implication

Cite This Study

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