Table 1.
Levels of Total and Free 25-Hydroxyvitamin D and Vitamin D–Binding Protein, According to Race and Geographic Region.*
| Substance and Type of Assay | MrOS Study | MRC Study | ||
|---|---|---|---|---|
| White Men (N = 919) |
Black Men (N = 101) |
White Men (N = 18) |
Black Men (N = 19) |
|
| median (interquartile range) | ||||
| Total 25-hydroxyvitamin D (nmol/liter)† | 62.2 (50.4–73.4) | 38.4 (24.5–53.9) | 25.6 (22.8–36.2) | 65.1 (57.1–78.3) |
| Vitamin D–binding protein (µmol/liter) | ||||
| Polyclonal radial immunodiffusion | 5.11 (4.69–5.48) | 5.08 (4.67–5.48) | 5.22 (4.79–5.48) | 4.79 (4.46–5.31) |
| Polyclonal ELISA: GenWay‡ | 4.79 (4.29–5.31) | 5.33 (5.00–5.69) | ND | ND |
| Polyclonal ELISA: Immundiagnostik‡ | ND | ND | 6.77 (6.60–7.58) | 6.65 (6.10–7.17) |
| Monoclonal ELISA: R&D Systems† | 4.86 (3.94–6.15) | 1.77 (1.34–3.25) | 5.50 (4.04–6.19) | 1.94 (1.64–3.85) |
| Calculated free 25-hydroxyvitamin D (pmol/liter)§ | ||||
| Polyclonal radial immunodiffusion† | 27.2 (22.5–32.5) | 17.3 (10.3–23.1) | 11.2 (9.4–18.1) | 31.4 (24.7–37.7) |
| Polyclonal ELISA: GenWay† | 29.0 (23.3–34.5) | 16.8 (9.7–22.1) | ND | ND |
| Polyclonal ELISA: Immundiagnostik† | ND | ND | 8.7 (6.7–13.7) | 23.8 (20.4–27.9) |
| Monoclonal ELISA: R&D Systems¶ | 28.1 (21.7–35.8) | 31.3 (19.8–50.6) | 12.0 (8.5–18.7) | 56.9 (45.1–69.2) |
| Directly measured free 25-hydroxyvitamin D: Future Diagnostics and DIAsource (pmol/liter)†‖ |
13.2 (11.0–16.5) | 9.0 (7.5–11.5) | 7.1 (5.5–8.3) | 16.0 (14.1–20.4) |
The Osteoporotic Fractures in Men (MrOS) study involved men 65 years of age or older in the United States, and the Medical Research Council (MRC) study involved men between the ages of 25 and 39 years in the United Kingdom and Gambia. P values for all listed comparisons in each study were performed by means of the Wilcoxon rank-sum test. P>0.10 for all comparisons with no P value indicated. To convert the values for total 25-hydroxyvitamin D to nanograms per milliliter, divide by 2.496. ND denotes not done.
P<0.001 for the comparisons between the two groups in both studies.
P<0.001 in the MrOS study and P = 0.30 in the MRC study.
Findings with respect to free 25-hydroxyvitamin D were similar to those for calculated bioavailable 25-hydroxyvitamin D (r = 0.99).
P = 0.04 in the MrOS study and P<0.001 in the MRC study.
For directly measured free 25-hydroxyvitamin D in the MrOS study, the evaluations were performed in 194 non-Hispanic white men and 80 black men.