ESPN 51th Annual Meeting

ESPN 2018

Differences in Serum 25 (OH) - Vitamin D binding protein level between African American (AA) and Caucasian (CS) children


In our previous pilot study investigating the normal value of 25(OH)D level in children, we identified significant differences between the levels based on ethnicity. This data correlates with previous finding in adults of lower 25(OH)D level in African American (AA) compared with Caucasians (CS). AA has lower 25(OH)D levels, while higher bone mineral density and lower risk for fractures as compared with CS. The above discrepancy is suspected to be due to possible differences in level of vitamin D 25-OH binding protein and their effect on free 25(OH)D.

Material and methods:

As part of their regular clinical care, we collected blood samples from 58 CS and 33 AA children (ages 1-18 years old) that were simultaneously analyzed for 25(OH)D, PTH, Ca and creatinine (Cr) between June, 2016 to October. In case of multiple measurements on a child only the initial value was included in the analysis. Children’s age, gender, ethnicity, serum Ca, serum Phosphorous and PTH levels were recorded. Serum 25(OH)D is measured by Tandem Mass Spectrometry on Applied Biosystems 4000QTrap (normal ≥30 ng/mL), PTH (normal 7-75 pg/mL) by immunoassay (Siemens ImmuliteTM), Ca and Cr are measured on Ortho’s Vitros autoanalyzer with age appropriate reference range. We excluded children with PTH ≥200 pg/mL. To exclude children with possible renal dysfunction we included children whose serum Cr are ≤0.6 mg/dL. Vitamin D 25-OH binding protein was measured by Pan Laboratories (15375 Barranca Parkway, Suite E-101, Irvine, CA 92618).


The mean 25(OH)D levels of CA and AA were not significantly different (40.62 ± 12.42 and 38.85 ± 15.637 respectively) as well there was no significant difference in mean Ca (9.88 ± 0.53 mg/dl and 9.74 ± 1.05 mg/dL respectively), phosphorus (5.01 ± .82 mg/dL and 5.11 ± 1.26 mg/dL respectively) and PTH (39.967± 28.25 and 52.059 ± 33.28 respectively). There was a significant difference between the mean Vitamin D 25-OH binding proteins of CS and AA children (347.91 ± 97.20 and 409.72 ± 121.33 respectively) p=0.009, 95% CI: (107.94- 15.65).


Our study demonstrated lower mean serum Vitamin D 25-OH binding protein in AA. This may affect the way vitamin D homeostasis is managed in various ethnic groups and may induce the need to explore the possibility that free 25(OH)D might be a better indicator of vitamin D status rather than total 25(OH)D.