NCSS 2007 (NCSS Statistical Software, Kaysville, UT, USA) was used for statistical analysis. The Shapiro-Wilk test was used to determine whether quantitative variables complied with normal distribution. For comparisons of quantitative variables between two groups, the Student t-test was used for variables that showed normal distribution and the Mann-Whitney U test was used for variables that did not show normal distribution. The Pearson chi-square test and Fisher exact test were used to compare qualitative data. Values of p<0.05 were considered statistically significant. The Cohen effect size for serum TXB2 was found to be 0.63. With that effect size, the power of the study in post hoc analysis was 81% for an error rate of 0.05 with 38 and 30 patients in the two groups according to G*Power 3.1.9.4 (Dusseldorf University, Dusseldorf, Germany).