Statistical analysis
All data were analyzed using GraphPad Prism 7 software (GraphPad, San Diego, California). Normality of variables was evaluated using Shapiro-Wilk test. Student’s unpaired t-test was performed for two-group comparisons of the data with normal distribution, otherwise Mann-Whitney U test was used. In addition, the interaction between variables was assessed by Pearson’s /Spearman’s correlation test, which was appropriate for normally and abnormally distributed variables respectively. P values of less than .05 indicated statistical significance.