To provide a solid background for our power analysis, we re-analyzed a large retrospective transplant cohort (transplantation and follow-up at the Medical University Vienna. Evaluating the impact of late (> 6 months) (C4d-positive) AMR on the clinical performance of kidney allografts a GFR slope of -8.2 ml/year (over a follow-up of 6 years), as compared to a slope of -1.8 ml/min/year in non-biopsied and -2.8 ml/min patients in biopsied C4d-negative subjects was observed.