Franny Jongbloed

220 CHAPTER 8 Statistical analysis Categorical data are presented as numbers (percentage) and continuous variables as median ± interquartile range (IQR). The data were tested for normality using the Shapiro– Wilks test and subsequent visual assessment. Continuous data were compared using the non-parametric Mann–Whitney U test. A Bonferroni correction for multiple testing was performed on the postoperative kidney function parameters. In the living kidney donors, this correction was done separately for the short-term outcome until POD3 and the long- term outcome until POMo3. In the transplant recipients, the cutoff for short-term outcome was set at POD7, and the cutoff for the long-term outcome on POMo6. To assess changes in GFR and creatinine levels over time for both donors and recipients, lme4 (Bates, Maechler & Bolker, 2012) for R 3.3.3 was used to perform a linear mixed effects analysis of the relationship between the outcomes of interest and treatment category. Random intercepts per patient were modelled. Visual inspection of residual plots did not reveal any obvious deviations from homoscedasticity or normality. Significance for the linear mixed-effects model analysis was set at P< 0.05 with t-tests using Satterthwaite approximations to degrees of freedom. The analyses were performed using Statistical Packages for Social Sciences 23.0 (IBM Inc., Chicago, IL, USA), R (R foundation), GraphPad Prism (GraphPad Software Inc., version 5.01), and Office Excel (Microsoft (Office) 2016).