Analysis was carried out with the use of SPSS statistical software package (SPSS version 17.01; SPSS, Chicago, IL, USA). Continuous variables were expressed as mean ± SD or median (with interquartile ranges). For categorical variables, the percentages of patients in each category were calculated. Unpaired t-test was used in normally distributed parameters to compare the mean values between the two groups. A p value of less than 0.05 was considered to indicate statistical significance.