Statistical analysis
Before commencing any statistical processing and analysis, data were
visually inspected and checked for outliers. The analysis was performed
using the commercial software Statistical Package for Social Science
(SPSS version 24.0, IBM, Chicago, IL, USA). Categorial variables were
tested using the chi-square test or Fisher’s exact test, as appropriate.
Continuous variables were examined using the student’s t test if
normally distributed and Man–Whitney test if not. To identify variables
associated with the primary outcome measure, univariate analysis was
performed. Variables that were significantly associated
(p<0.05) with the primary outcome measure (defined as the
composite endpoint of death or requirement for mechanical ventilation
during hospitalization) were entered into the multivariate logistic
regression model in a stepwise fashion. Adjusted odds-ratios (ORs) and
95% confidence intervals (CIs) for the likelihood of occurrence of
primary outcome measure were calculated. Statistical significance was
set at p-value less than 0.05.