Association of vitamin D status with COVID-19 disease severity in pediatric patients: A retrospective observational study

Background and Aims Vitamin D deficiency is associated with increased vulnerability to respiratory infections. This study aimed to determine the potential relationships between coronavirus disease 2019 (COVID-19) severity, serum vitamin D concentrations, and some inflammatory markers among pediatric COVID-19 patients in Iran. Methods A retrospective study was conducted among hospitalized pediatric COVID-19 cases in Abuzar Hospital (Ahvaz, Iran) for 6 months. The COVID-19 diagnosis was based on the real-time reverse transcription-polymerase chain reaction technique. Demographic and clinical data of patients were recorded. Patients with serum vitamin D levels lower than 20 ng/ml were assigned as Group 1 and those with serum vitamin D concentrations equal to or more than 20 ng/ml were considered as Group 2. Results A total of 144 patients were enrolled. Their mean age was 80 +/- 49 months (range: 1-16 years). Patients in Group 1 had significantly lower levels of serum vitamin D, calcium, and lymphocytes, as well as higher fibrinogen, d-dimer, and C-reactive protein (CRP) levels compared with those in Group 2 (p < 0.001). In addition, they had a significantly higher dry cough, fever, chest radiographic findings, respiratory rate, and longer hospital length of stay than patients in Group 2. Serum concentrations of vitamin D were positively correlated with levels of serum calcium, lymphocytes, and neutrophils but negatively correlated with CRP, fibrinogen, and d-dimer values. Furthermore, patients with moderate or severe courses of COVID-19 had significantly higher inflammatory markers (CRP, d-dimer, and fibrinogen), as well as lower levels of serum calcium, vitamin D, lymphocytes, and neutrophils than those with mild COVID-19 (p < 0.001). In the multivariate analysis, fibrinogen level on admission was detected as the independent predictor of severe COVD-19 (odds ratio = 1.06, 95% confidence interval: 1.03-1.09; p < 0.001). Conclusion This study indicated associations between the severity of COVID-19, serum vitamin D concentrations, and some inflammatory markers in pediatric COVID-19 patients.