The association between vitamin D levels and the clinical severity and inflammation markers in pediatric COVID-19 patients: single-center experience from a pandemic hospital

Vitamin D has an immunomodulating property that regulates the inflammatory response. In this study, the aim was to evaluate the relationship between vitamin D levels and clinical severity and inflammation markers in children and adolescents with COVID-19. The clinical and laboratory records of 103 pediatric cases with COVID-19, whose vitamin D levels had been measured, were retrospectively reviewed. The cases were divided into groups according to their clinical severity (asymptomatic, mild, and moderate-to-severe) and vitamin D levels. The moderate-to-severe clinical group had significantly higher inflammation markers (CRP, procalcitonin, fibrinogen, d-dimer) and a lower lymphocyte count compared to both the mild and asymptomatic groups. The 25 OH vitamin D levels were also significantly lower (p < 0.001), and the ratio of vitamin D deficiency was 70.6% in the moderate-to-severe group. The vitamin D–deficient group had a significantly higher age and fibrinogen levels while also having a lower lymphocyte count compared to the insufficient and normal groups. The 25 OH vitamin D level was correlated positively with the lymphocyte count (r = 0.375, p = <0.001), and negatively with age (r = −0.496, p = <0.001), CRP (r = −0.309, p = 0.002) and fibrinogen levels (r = −0.381, p = <0.001). In a logistic regression analysis, vitamin D deficiency, d-dimer, and fibrinogen levels on admission were independent predictors of severe clinical course. Conclusion: This study revealed an association between vitamin D deficiency and clinical severity, in addition to inflammation markers in pediatric COVID-19 cases. Prophylactic vitamin D supplementation may be considered, especially in the adolescent age group. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00431-021-04030-1.