Relationship between serum 25-hydroxyvitamin D concentration and acute inflammatory markers in hospitalized patients with SARS-CoV-2 infection

INTRODUCTION: There is experimental and clinical evidence that the serum concentration of 25-hydroxyvita­min D [25(OH)D)] may decrease in acute systemic inflammatory responses; in this context, low values may not necessarily indicate a pre-existing deficiency. This may also apply to low 25(OH)D levels found in the context of the systemic inflammatory response caused by SARS-CoV-2 infection. To conduct a systematic review of the relationship between serum 25(OH)D and the concentrations of C-re­active protein (CRP), interleukin 6 (IL-6) and tumour necrosis factor a (TNF-a) in acutely hospitalized patients with SARS-CoV-2 infection. MATERIAL AND METHODS: We searched PubMed, EMBASE, Google Scholar and the Cochrane Database of Systematic Reviews for studies published between January 2020 and February 2021. In each study, the au­thors compared levels of inflammatory markers between patients reported as having low levels of 25(OH) D and those above the study cut-off. RESULTS: 18 studies were included (n = 3482, mean age 63.5 ± 9.3 years, 56.9% men). The cut-off for the definition of low 25(OH)D varied across studies. In all studies, mean values for inflammatory markers were higher in the low 25(OH)D groups. These differences were statistically significant (p < 0.05) in 6/15 studies with CRP, 4/8 with IL-6 and 0/1 with TNF-a. CONCLUSIONS: Markers of acute systemic inflammatory response were elevated in patients with SARS-CoV-2 infection and low concentrations of 25(OH)D. Therefore, the vitamin D status in those patients should be interpreted with caution, and studies should be designed to assess whether hypovitaminosis D could be an epiphenomenon.