Sample Size: There are few data in the literature on which to base a sample size calculation for the composite outcome selected. Based on historical data, which indicated an event rate > 50%, we calculated a sample size designed to detect an effect of plasma exchange on dialysis dependence, without informative censoring from death, at 6 months. In order to detect a difference of 50% in that outcome with a type 1 error of 0.05 (two-sided) and a type 2 error probability of 0.20, the sample size requirement was 46 per group. We will use this historical based power analysis to provide a conservative estimate of sample size to detect a statistically significant difference in the composite outcome of death, dialysis dependence or a GFR of < 30ml/min/1.73m2 in our future study.