Vitamin D deficiency increases the susceptibility to respiratory virus infections and the severity of infections. Inflammation plays a key role in pathogenesis in COVID19 while identifying clinical course and prognosis COVID19.The aim of this study was to determine the relationship between 25OH vitamin D levels, inflammatory laboratory parameters of neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), C-reactive protein (CRP) levels and disease severity of COVID19 infection.

In this retrospective study 300 patients diagnosed with COVID19 were included. According to clinical classification of cases with COVID19 the patients were divided into three groups; mild (Group1), moderate (Group2) and severe/critical (Group3). The 25OH vitamin D values below 20 ng/ml were defined as deficiency, 21-29 ng/ml were defined as insufficiency, and 30 ng/ml and above were defined as normal. Patients' age, gender, comorbid diseases and laboratory values were recorded

Inclusion Criteria:

• The study included 300 polymerase chain reaction (PCR) test positive patients and whose 25-OH vitamin D levels were measured in the last 6 months

Exclusion Criteria:

• Patients with COVID-19 whose 25-OH vitamin D levels were not measured in the last 6 months before the COVID-19 diagnosis were excluded from the study

COVID19 infection positive patients whose polymerase chain reaction (PCR) test positive patients and whose 25-OH vitamin D levels were measured in the last 6 months