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Table 2 Sample size justification

From: Inhibiting the progression of arterial calcification with vitamin K in HemoDialysis patients (iPACK-HD) trial: rationale and study design for a randomized trial of vitamin K in patients with end stage kidney disease

Control arm CAC progression rate Relative risk reduction Phylloquinone arm progression rate Sample size per arm for 80% power
80 20% 64% 123
70 20% 56% 186
60 20% 48% 270
50 20% 40% 388
80 25% 60% 80
70 25% 53% 121
60 25% 45% 173
50 25% 38% 247
RRR = Relative risk reduction   
  1. Estimate of the power for testing the effect of the intervention. The effect sizes are described in terms of relative risk reduction for a > 15% increase in CAC score over baseline in 12 months. The bolded row indicates estimates utilized for sample size calculation for the iPACK-HD trial.