Can Serum 25-Hydroxy Vitamin D Levels Predict the Severity of Multisystem Inflammatory Syndrome in Children and COVID-19?

Objective: To determine the clinical significance of serum 25-hydroxy (OH) vitamin D levels in pediatric patients with multisystem inflammatory syndrome in children (MIS-C) and compare the vitamin D levels of these patients with those patients with Coronavirus disease-2019 (COVID-19) and healthy controls. Methods: This study was designed for pediatric patients aged 1 month to 18 years and conducted between July 14 and December 25, 2021. Fifty-one patients with MIS-C, 57 who were hospitalized with COVID-19, and 60 controls were enrolled in the study. Vitamin D insufficiency was defined as a serum 25 (OH) vitamin D level of less than 20 ng/mL. Severe MIS-C was classified as necessitating intensive care due to cardiovascular instability, the necessity for non-invasive or invasive mechanical ventilation, and/or a diminishing Glasgow coma scale. World Health Organization definition criteria were used to describe the clinical stages of COVID-19 in children and patients were divided into four groups according to the clinical severity of COVID-19: asymptomatic, mild, moderate, and severe/critical. Results: The median serum 25 (OH) vitamin D was 14.6 ng/mL in patients with MIS-C, 16 ng/mL in patients with COVID-19, and 21.1 ng/mL in the control group (p<0.001). Vitamin D insufficiency was present in 74.5% (n=38) of patients with MIS-C, 66.7% (n=38) of patients with COVID-19, and 41.7% (n=25) of the controls (p=0.001). The percentage of four or more affected organ systems was 39.2% in patients with MIS-C. The correlation between the number of affected organ systems and serum 25 (OH) vitamin D levels was evaluated in patients with MIS-C and there was a moderate negative correlation (r=-0.310; p=0.027). A weak negative correlation was found between the severity of COVID-19 and serum 25 (OH) vitamin D (r=-0.320, p=0.015). Conclusion: Vitamin D levels were insufficient in both the MIS-C and COVID groups. Furthermore, vitamin D levels correlated with the number of affected organ systems in MIS-C and the severity of COVID-19.