Marker of vitamin D status in healthy children: Free or total 25-hydroxyvitamin D?

PLoS One. 2018 Aug 23;13(8):e0202237. doi: 10.1371/journal.pone.0202237. eCollection 2018.

Abstract

Objective: To assess if serum free 25-hydroxyvitamin D (25OHD) is a better indicator of vitamin D status than total 25OHD in healthy children.

Methods: Cross-sectional prospective clinical study was designed. We measured serum free 25OHD concentrations and its correlation with calculated free 25OHD, total 25OHD, intact parathyroid hormone (PTH), and vitamin D binding protein (DBP) in children. The influence of age, sex, ethnicity, body mass index (BMI), season of the year, diet intake, vitamin supplements, time spent outdoors and albumin concentrations on free 25OHD was also analyzed. 241 children aged from 0 days to 14 years, and living in the northern Spain (latitude 43° N), were included.

Results: Mean (SD) free 25OHD concentrations were 2.48 (1.39), 5.46 (3.12), 4.12 (1,72), 3.82 (1.43) pg/ml in children aged 0 days, 1 month-2 years, 2-6 years and >6 years, respectively. Correlation between directly measured and calculated free 25OHD was high and significant (r = 0.66) as well as the correlation between serum free and total 25OHD concentrations (r = 0.61). No significant correlation was found between PTH and free 25OHD (r = -0.08). The total 25OHD and PTH concentrations' correlation was inverse (r = -0.25) and significant. Neither free nor total 25OHD concentrations correlated with DBP concentrations. Among the analyzed variables, free 25OHD values were higher in spring/summer than in autumn/winter in children older than 6 years.

Conclusions: : These findings do not support that free 25OHD is a better marker of vitamin D deficiency than total 25OHD in healthy pediatric population.

Publication types

  • Clinical Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Biomarkers / blood
  • Child
  • Child, Preschool
  • Cross-Sectional Studies
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Parathyroid Hormone / blood
  • Prospective Studies
  • Reference Values
  • Seasons
  • Serum Albumin, Human / metabolism
  • Spain
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D-Binding Protein / blood

Substances

  • Biomarkers
  • GC protein, human
  • PTH protein, human
  • Parathyroid Hormone
  • Vitamin D-Binding Protein
  • Vitamin D
  • 25-hydroxyvitamin D
  • Serum Albumin, Human

Grants and funding

This research study was supported by PI15/02122 (Plan Estatal I+D+I 2013-2016) grant from the Instituto de Salud Carlos III (Spain) (FS) and fondos FEDER; by GRUPIN 14-020, grant from Hospital Universitario Central de Asturias and by grant from the Foundation “Ernesto Sánchez-Villares”, and the Foundation “Nutrición y Crecimiento”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.