Background: The aim of this study was to assess the relationship between vitamin D status and the prevalence of dyslipidemia and impaired fasting glucose (IFG) in children. Methods and Summary: 284 children (150 boys and 134 girls) aged 9–11 were included in the study. Children with deficient 25(OH)D (25-hydroxycholecalciferol) levels ≤20 ng/mL (50 nmol/L) were characterized by a more frequent occurrence of impaired fasting glucose (IFG) (Odd ratios (OR) = 1.966, 95% confidence interval (CI): 1.055–3.663; p = 0.033) when compared to children with 25(OH)D >20 ng/mL. Serum 25(OH)D with concentration lower by 1 ng/mL (2.5 nmol/L) was linked to higher fasting glucose (by 0.25 mg/dL, 0.013 mmol/L; p = 0.017), higher total cholesterol (TC) by almost 1 mg/dL (0.96 mg/dL, 0.25 mmol/L; p = 0.006) and higher high-density lipoprotein cholesterol (HDL-C) (by 0.57 mg/dL, 0.015 mmol/L; p < 0.001). Conclusion: 25(OH)D deficiency may negatively affect fasting glucose and total cholesterol concentration in children aged 9–11. Vitamin D-deficient children are twice as likely to develop prediabetes as reflected by impaired fasting glucose when compared to those with a 25(OH)D level above 20 ng/mL (50 nmol/L).

Both vitamin D and insulin-like growth factor 1 (IGF-1) play essential roles in bone metabolism and may interact during prepubertal bone accrual. We investigated the association of low serum 25-hydroxyvitamin D (25(OH)D) (<20 ng/mL) with the circulating bone turnover markers, when compared to their interaction with IGF-1. Subjects and Methods: Serum 25(OH)D, IGF-I, P1NP (N-terminal propeptide of type I procollagen), and CTX-1 (C-terminal telopeptide of type I collagen) were measured, and the bone turnover index (BTI) was calculated in 128 healthy children, aged 9–11 years. Results: Mean 25(OH)D concentration was 21.9 ± 4.9 ng/mL, but in 30.5% of participants it was <20 ng/mL (<50 nmol/L). We observed a trend for higher P1NP (p < 0.05) and IGF-1 (p = 0.08), towards lower 25(OH)D in tertiles. Levels of P1NP in the lowest 25(OH)D tertile (<20 ng/mL) were the highest, while CTX and BTI remained unchanged. Additionally, 25(OH)D negatively correlated with IGF-1, while the correlation with P1NP was not significant. A strong positive correlation of IGF-1 with P1NP and BTI but weak with CTX was observed. Low 25(OH)D (<20 ng/mL) explained 15% of the IGF-1 variance and 6% of the P1NP variance. Conclusions: Low levels of 25(OH)D do not unfavorably alter bone turnover. It seems that serum 25(OH)D level may not be an adequate predictor of bone turnover in children.

Over the last decade interest in automated assays for 25-hydroxy-vitamin D measurement have greatly increased. The presence of different metabolites of vitamin D in the blood influences measurement of its concentration. In paediatric subjects the basic interference is due to the presence of 3-epi-25(OH)D2/D3, which despite their biological inactivity, influences the total concentration of 25(OH)D. Aim: We assessed the analytical performance and usefulness of two different assays for measurement of total 25(OH)D in children. Materials and Methods: The study was performed in blood samples taken from 100 school-children aged 9–11 years. In all serum samples 25(OH)D total concentration was measured with the use of chemilumi-nescent assay, which is known to show no cross-reactivity with 3-epi-25(OH)D, and with the use of a newly developed enzyme-immunosorbent method. Results: The mean 25(OH)D concentration in children measured with enzyme-immunosorbent assay (EIA) was significantly higher, at 28.06 ng/mL, than with the chemiluminescent assay (CLIA), at 21.13 ng/mL; < 0.0001. In children with optimal weight the average 25(OH)D was 32.93 ng/ml (EIA) and 21.5 ng/mL (CLIA) (p < 0.0001), respectively, whereas in a subgroup with overweight/obesity the mean concentra-tion of 25(OH)D was similar, at 23.2 ng/ml (EIA) and 20.76 ng/ml (CLIA) (p = 0.15). The nonparametric Spearman’s rank correlation of two methods equalled 0.47; 95%CI (0.11 to 0.60) with a significance level p < 0.0001. The calculated concordance correlation coefficient between two methods in the whole group was 0.26; 95%CI (0.17 to 0.35). In a subgroup of children with optimal body mass (N = 50) the concor-dance correlation coefficient was 0.18; 95%CI (0.06 to 0.29), whereas in children with overweight/obesity (N = 50) it was 0.44; 95%CI (0.29 to 057). Mean bias for the enzyme-immunosorbent method equalled 18.7%; +/- 1.96 SD (101.3% to -64%). Conclusions: With reference to 25(OH)D measurement in children, Spearman’s correlation coefficient indicated “moderate correlation” between the two compared methods, whereas the strength of agree-ment (concordance) between both methods was characterised as “poor”. The proper selection of assay for accurate assessment of vitamin D status in paediatric samples is necessary to avoid misdiagnosis. Over the last decade interest in automated assays for 25-hydroxy-vitamin D measurement have greatly increased. The presence of different metabolites of vitamin D in the blood influences measurement of its concentration. In paediatric subjects the basic interference is due to the presence of 3-epi-25(OH)D2/D3, which despite their biological inactivity, influences the total concentration of 25(OH)D. Aim: We assessed the analytical performance and usefulness of two different assays for measurement of total 25(OH)D in children. Materials and Methods: The study was performed in blood samples taken from 100 school-children aged 9–11 years. In all serum samples 25(OH)D total concentration was measured with the use of chemilumi-nescent assay, which is known to show no cross-reactivity with 3-epi-25(OH)D, and with the use of a newly developed enzyme-immunosorbent method. Results: The mean 25(OH)D concentration in children measured with enzyme-immunosorbent assay (EIA) was significantly higher, at 28.06 ng/mL, than with the chemiluminescent assay (CLIA), at 21.13 ng/mL; < 0.0001. In children with optimal weight the average 25(OH)D was 32.93 ng/ml (EIA) and 21.5 ng/mL (CLIA) (p < 0.0001), respectively, whereas in a subgroup with overweight/obesity the mean concentra-tion of 25(OH)D was similar, at 23.2 ng/ml (EIA) and 20.76 ng/ml (CLIA) (p = 0.15). The nonparametric Spearman’s rank correlation of two methods equalled 0.47; 95%CI (0.11 to 0.60) with a significance level p < 0.0001. The calculated concordance correlation coefficient between two methods in the whole group was 0.26; 95%CI (0.17 to 0.35). In a subgroup of children with optimal body mass (N = 50) the concor-dance correlation coefficient was 0.18; 95%CI (0.06 to 0.29), whereas in children with overweight/obesity (N = 50) it was 0.44; 95%CI (0.29 to 057). Mean bias for the enzyme-immunosorbent method equalled 18.7%; +/- 1.96 SD (101.3% to -64%). Conclusions: With reference to 25(OH)D measurement in children, Spearman’s correlation coefficient indicated “moderate correlation” between the two compared methods, whereas the strength of agree-ment (concordance) between both methods was characterised as “poor”. The proper selection of assay for accurate assessment of vitamin D status in paediatric samples is necessary to avoid misdiagnosis.