Statistical analysis
Categorical variables were expressed as numbers and percentages and compared using the Pearson Chi square test or Fisher’s exact test as suitable. Continuous variables were expressed as mean ± standard deviation if normally distributed otherwise as median (1st and 3rd quartiles) and compared using Student’s t-test or non-parametric Mann-Whitney test as needed. Association between baseline characteristics and the occurrence of clinical event was evaluated by univariate analysis. Variables with p value ≤0.20 in the univariate analysis were introduced in the multivariate analysis using a binary logistic regression model with Wald’s step-by-step method. Statistical significance was set at a two-tailed probability level of <0.05. All analyses were performed using IBM SPSS Statistics for Windows version 23.0 (released 2015, IBM SPSS Statistics for Windows, IBM Corp., Armonk, NY, USA).