Abstract:

Aim: This study aimed to examine the status of vitamin D in children, to compare vitamin D levels according to the seasons, and to estimate vitamin D testing trends during the years of the study. Materials and Methods: Blood 25-hydroxyvitamin D [25(OH)D] levels of 51,560 children aged between 0-18 years who had been admitted to nine hospitals between 2015 and 2017 were evaluated. Comparisons of 25(OH)D levels with age groups, gender, and seasons were made. Additionally, vitamin D testing was compared year by year in terms of frequency. Results: Of the patients, 20% (n=10,611) had vitamin D deficiency and 34% (n=17,385) had vitamin D insufficiency. Serum 25(OH)D levels were significantly higher in boys than in girls (p<0.01). There was a significant difference between serum 25(OH)D levels and the age groups. The highest mean 25(OH)D levels were detected in infants (33.95 ng/mL) and the lowest in adolescents (18.3 ng/mL). Significant seasonal variability of 25(OH)D levels was detected (p<0.01). Vitamin D deficiency was determined most frequently in winter with a frequency of 30.7%. A three-fold increase in 25(OH)D testing was determined over the 3-year period. Conclusion: Female gender, adolescence, and the winter season were found to be important risk factors for vitamin D deficiency or insufficiency. Further evidence is needed to clarify whom to test in order to avoid over-testing.

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