The establishment of serum 25-hydroxyvitamin D reference intervals in children aged 0–14 years in Zigong area, China

Abstract

Objective To establish the reference interval of serum 25-hydroxyvitamin D (25(OH)D) in apparently healthy children in Zigong, China, using an indirect method to provide a basis for proper clinical diagnosis and treatment. Methods A total of 1851 apparently healthy children of the Children’s Health Care Department in Zigong First People’s Hospital between January 2016 and December 2020 were included in the study. The Kolmogorov–Smirnov test was used to analyze the data for normality, and the non-normally distributed data were transformed into approximately normal distribution by Blom's normal rank transformation, and the transformed data were excluded from outliers by the quartile spacing method, and the data were stratified and analyzed according to sex, age, and season. The data were stratified according to sex, age, and season, and the area between the 2.5% and 97.5% percentile points was used as the reference interval. Results The serum 25(OH)D data were non-normally distributed. The data were normally distributed after Blom’s normality rank transformation, and 92 cases of outliers were excluded from the transformed data according to the interquartile spacing method. The differences in serum 25(OH)D levels between sex were not statistically significant (P > 0.05), and there was no need to establish reference intervals based on sex. There was no statistically significant difference in serum 25-hydroxyvitamin D levels between winter and spring, and also no difference between summer and autumn (P > 0.05), and the levels were lower in winter-spring than in summer-autumn. Comparison between age groups showed that there was no statistically significant difference in serum 25(OH)D levels between the < 6 months group and the 6 ~ 11 months group, and between the 6 ~ 9 years group and the 10 ~ 14 years group (P > 0.05); serum 25(OH)D levels decreased with increasing age. There was an interactive effect of season and age group on 25(OH)D levels, and the corresponding reference intervals were established according to different seasons and age groups. In summer and autumn, the reference intervals of serum 25(OH)D for < 1 year, 1 ~ 2 years, 3 ~ 5 years, and 6 ~ 14 years were 39.86 ~ 151.43, 31.54 ~ 131.65, 22.05 ~ 103.75, and 15.36 ~ 85.53 ng/ml and 24.42 ~ 144.20, 31.54 ~ 131.65, 16.80 ~ 165.68, and 15.46 ~ 85.54 ng/ml in winter and spring, respectively. Conclusion Reference intervals for serum 25(OH)D in children of different seasons and ages in Zigong, China, were established to provide a reference for clinical disease diagnosis, treatment, and prognosis determination.

Age-, season- and gender-specific reference intervals of serum 25-hydroxyvitamin D3 for healthy children (0 ~ 18 years old) in Nanning area of China

“…Our findings indicated that there were statistically significant variations in the 0 ~ ≤ 1 year, 2 ~ ≤ 3 years, 4 ~ ≤ 6 years, and 7 ~ ≤ 18 years age groups (all P < 0.001), and the serum 25(OH)D levels decreased with age increasing, which is in agreement with prior studies [ 17 – 19 ]. The trend may be attributed to the young children's daily intake of vitamin D-rich infant formula as well as fortified baby foods, while adolescents' lack of outdoor activities and inadequate vitamin D supplementation.…”

“…It was discovered that the serum 25(OH)D levels during summer were significantly lower compared to autumn, while higher than in winter (all P < 0.001). The findings for the seasonal fluctuation in serum 25(OH) levels were close to those from other research projects carried out in the Zigong area and southern China [ 17 , 20 ]. The varying levels of 25(OH)D can be explained by the amount of sunlight exposure, since it is mainly acquired through exposure to the sun's UV rays that activate its production in the skin.…”