Serum vitamin D and vitamin D receptor (VDR) polymorphisms (FokI and TaqI) as predictors of COVID19 severity. ( Prospective study in a cohort of Egyptian COVID-19 patients)

Background: Severe forms of respiratory failure affect 20% of COVID‐19 patients with a death rate of about 65%. Vitamin D deficiency and vitamin D receptor polymorphisms, mainly Taql (rs731236) and Fokl (rs10735810), were associated with respiratory tract infections. Methods: A prospective study on 90 confirmed PCR-positive COVID-19 patients was done. Results: Statistically significant lower levels of 25OH vitamin D were found in severe to critical COVID-19 and non-survivors than in mild to moderate patients and survivors (p < 0.001) and with negative correlations with C-reactive protein, ferritin, procalcitonin, interleukin 6, D-dimer, INR, white blood cells, neutrophils count, and neutrophils/lymphocytes ratio. Serum 25(OH) D was positively correlated with oxygen saturation level, hemoglobin, lymphocyte, and monocyte counts. Mild to moderate and severe to critical patients showed significant differences in both FokI SNP (p = 0.002) and TaqI genotypes (p = 0.010). FokI recessive mode might be associated with increased severity, while TaqI dominant mode of inheritance and the mutant allele (t) might protect against severe forms of COVID-19. Conclusion: 25 OH D and FokI recessive mode of inheritance may be associated with severe forms of COVID-19; however, TaqI dominant mode of inheritance and the mutant allele (t) might protect against COVID-19 severity. It is recommended to apply similar research on different populations together with studying other VDR polymorphisms in addition to clinical trials of vitamin D supplementation in order to generalize these findings.