STATISTICAL ANALYSIS
We used a certified statistical program, MedCalc version 13.1.2. (VAT registration no. BE 0809 344 640, Member of International Association of Statistical Computing, Ostend, Belgium), to perform statistical analyses. Continuous data were compared using the Student’s t-test or the Wilcoxon rank-sum test as appropriate. The χ2 test and Fisher’s exact test were used for categorical variables. Univariate and multivariate logistic regressions were used to assess monitored parameters in order to predict the risk of severe course and death. Statistically significant parameters assessed in the univariate analysis were entered in the multivariate model. Statistically significant parameters were also further analysed by the means of probit regression. We considered the P-value of < 0.05 to be statistically significant.