Statistical analysis
The data were presented as the mean ± standard deviation (SD) for continuous variables or as number and percentages (%) for categorical variables. For continuous and categorical variables, differences between the two groups were compared using the Student’s t -test, Mann–Whitney U test, and Fisher’s exact test, respectively. All tests were two sided and a P value of <0.05 was considered statistically significant. All statistical analyses were conducted using SPSS version 21.0 (IBM Corp., Armonk, NY, USA).