BACKGROUND: The aim of this study was to investigate changes in some laboratory 
parameters in response to four independent variables (COVID-19, diabetes, 
gender, and age) using univariate and multivariate analysis.
METHODS: We measured WBC (neutrophil and lymphocytes), RBC and platelet counts, 
and hemoglobin, lactate dehydrogenase, C-reactive protein, IL-2, IL-4, and 
vitamin D3 levels in 30 hospitalized patients with severe COVID-19 and in 30 
healthy people in terms of COVID-19. The population was divided into groups 
based on each of the variables of age, gender, COVID-19, and type 2 diabetes. 
Then they were subjected to univariate and multivariate analysis of logistic 
regression.
RESULTS: Based on CBC data, leukocytosis (in 70% of COVID-19 patients, 61.1% of 
diabetic patients, and 70.9 ± 18 years old), neutrophilia (in 73.3% of patients 
with COVID-19, 61.1% of diabetic patients, and 66 ± 18.6 years old), neutropenia 
(in 6.7% of patients with COVID-19, 27.8% of diabetic patients, and 33.6 ± 12.7 
years old), lymphocytosis (10% of patients with COVID-19, 33.3% of diabetic 
patients, and 35.4 ± 15.5 years old), and lymphocytopenia (in 76.7% of patients 
with COVID-19, 66.7% of diabetic patients, and 67.1 ± 18.8 years old) were 
observed in the population. The elderly and those with COVID-19 had significant 
abnormal RBC and platelet counts. Increased LDH and CRP levels and abnormal 
hemoglobin level were related to elderly, COVID-19, and diabetes conditions. 
Although the levels of IL-2 and -4 were significant in patients with COVID-19 
and elderly; however, the changes were not significant in diabetic patients. 
Changes in serum vitamin D levels were not significant in any of the sub-groups.
CONCLUSIONS: We showed that leukocytosis, neutrophilia, lymphocytopenia, 
abnormal counts of RBCs and platelets, the elevated levels of LDH and CRP, and 
abnormal hemoglobin levels in blood are considered as poor prognostic factors 
for COVID-19.