Planning and Conducting the ISCHEMIA Trial: Setting the Record Straight

David J. Maron, MD; Robert A. Harrington, MD; Judith S. Hochman, MD


Circulation. 2018;138(14):1384-1386. 

In This Article

Sample Size

The original estimated sample size was 8000, with projected power ≥90% if the 4-year event rate in the conservative strategy group was 20%, assuming a 15% risk reduction of the primary end point. Nonadherent cardiac catheterization rates in the conservative strategy in the absence of an end point event ranging from 30% to 70% were considered during study planning. By 2015, it was clear that we would not be able to randomize 8000 participants even with an extended recruitment period allowable by the available funding. On the positive side, with regard to power, the observed rate of nonadherent cardiac catheterization in the conservative strategy was much lower than projected. We proposed a plan to reduce the sample size from 8000 to 5000, extend recruitment by 6 months, and extend follow-up by 6 months. This proposal was approved by the NHLBI in 2016.