On 2017 Mar 02, Prajak Barde commented:

A study by Kaul U successfully concluded that paclitaxel-eluting stents failed to demonstrate non-inferiority against everolimus-eluting Stents that in diabetic patients undergoing PCI.

The trial was powered to detect non-inferiority on the basis of Spirit IV trait assuming that 1 year rate of target vessel failure of 8.4% with each stent, with non-inferiority margin of 4 %. However, documented failure rate in Spirit IV was 4.2 % in CAD patients and 6.4% in diabetic patients. Author did not explain the reason for these differences which potentially may lead to under powering of trial.

Author choose the margin (4%) based on Absolute risk difference that can result in under powering of the trial due to lower than expected event rates. Author might have foreseen the differences in the event rate however this was not justified why the sample size adjustment was made.

In the current the relative risk was inflated substantially increasing the risk of accepting the hypothesis of non-inferiority, which was not demonstrated due to clear differentiation of the effect.

On 2017 Mar 02, Prajak Barde commented:

A study by Kaul U successfully concluded that paclitaxel-eluting stents failed to demonstrate non-inferiority against everolimus-eluting Stents that in diabetic patients undergoing PCI.

The trial was powered to detect non-inferiority on the basis of Spirit IV trait assuming that 1 year rate of target vessel failure of 8.4% with each stent, with non-inferiority margin of 4 %. However, documented failure rate in Spirit IV was 4.2 % in CAD patients and 6.4% in diabetic patients. Author did not explain the reason for these differences which potentially may lead to under powering of trial.

Author choose the margin (4%) based on Absolute risk difference that can result in under powering of the trial due to lower than expected event rates. Author might have foreseen the differences in the event rate however this was not justified why the sample size adjustment was made.

In the current the relative risk was inflated substantially increasing the risk of accepting the hypothesis of non-inferiority, which was not demonstrated due to clear differentiation of the effect.