If we assume that the Sevelamer group ("treatment group") will have the same 9% decrease in PWV at 6 months, from baseline, the Ca-binder group ("control group") will have no change (i.e. no increase in PWV - "conservative approach", but different from Takenaka's results where an increase in PWV was reported - see above), the standard deviation of the PWV is 1.88 m/s in our experience or 1.3 m/s/mmHg, the ratio of 1 between the control and thre treatment arms, than for a power of 80% and a confidence interval of 95% we need 108 patients in each arm (105 if PWV/BP is used), 216 total. This will also have sufficient power detect a decrease in AIx of only 4.6% or 16.5% from baseline in the treatment arm. This is usually less than that recorded after different acute interventions (GTN, salbutamol, dialysis session) or after transplantation in HD patients.