Sample size {14}
1.1.2012
A total of 260 patients will be included in the trial, 130 in the active group and 130 in the control group. For the sample size calculation, we analysed the occurrence of the primary endpoint in recipients of a kidney allograft transplanted between 1.1.2012 and 31.12.2018 at the Medical University of Vienna, applying the trial-specific inclusion and exclusion criteria. Overall, 40% of patients experienced the primary endpoint between months 3 and 12 after transplantation (unpublished data). Therefore, we assume a composite rate of around 40% in the standard dosing (arm S). It is expected that the TTV-guided immunosuppression (arm T) reduces the occurrence of the primary endpoint, and therefore rates between 20 and 30% are assumed to be reasonable.The non-inferiority .margin has been fixed at 10% points. Thus when the sample size in each group is 120, a two-group large-sample normal approximation test of proportions with a one-sided 2.5% significance level will have 90.42% power to reject the null hypothesis that arm T is inferior to standard arm S in favour of the alternative hypothesis arm T is not inferior to arm S. Due to the planned observation period of 9 months and the special patient population, a rather low drop-out rate is expected of about 2–5%. Adjusting for potential drop-outs, the sample size is fixed with 130 patients per group, i.e., 260 in total. The sample size calculation was performed using N-Query Version 8.6.1.