Statistical analysis

All statistical tests were performed using GraphPad Prism software version 5 (GraphPad Inc., San Diego, CA, USA). Data that were not normally distributed were displayed as median along with interquartile ranges and were compared with Mann–Whitney U test for two group comparisons. The Gaussian data were reported as the mean ± standard deviation and were analysed using the t test for two group comparisons. Proportions were compared using the χ² test or the Fisher’s exact test, as appropriate. Correlations were determined using the Spearman test. A comparison was considered statistically significant if the p value was ≤0.05.