Spss vs 21.0

Statistical analysis was performed using SPSS (vs 21.0) and included descriptive statistics, cross-tabulations, relevant parametric/non-parametric tests and regression analyses. Continuous variables were tested for normal distribution by Kolmogorov–Smirnov test. For normal distributed continuous variables, means ± standard deviations were calculated. For non-normal distributed continuous variables, medians ± interquartile ranges (IQR) were calculated. Groups with continuous variables were compared with the t-test (normal distribution) or with the Mann–Whitney U test (non-normal distribution). Discrete variables were compared with the chi-square test. Odds ratios were calculated with a logistic regression model, and 95% confidence intervals were reported. Parameters were included in the multifactorial regression if the p value was < 0.1 in the univariate regression model. A two-sided p value < 0.05 was considered statistically significant.