Sample size and statistical analysis
tattoo, tumor
REGRESSION, TUMOR
The primary objective of this study is to identify non-inferiority of autologous blood tattooing versus intraoperative colonoscopy group. Based on our current experience and previous studies which reported the rates of successful visualization, success rates of 99 and 95% were assumed for the intraoperative colonoscopy group and the autologous blood group, respectively. With settings of 80% power, 5% significance level, and non-inferiority margin of 10%, sample sizes of 110 patients in each group will be required.Continuous variable will be presented as mean and SD if normally distributed, or as median and range otherwise. The differences between the groups were assessed using the t-test, the Mann-Whitney test, Fisher’s exact test, or the χ2 test, as appropriate. Multivariate analysis to assess the impact of potential con- founding factors (sex, age, body mass index, endoscopist, tumor location [colon vs. rectum], clinical tumor stage [≥ T2 vs. T1 or scars]) on invisible tattoo will be performed by using a logistic regression model. All tests will be two-sided with a significance level of 