To the Editor: In their study of transfusion requirements after cardiac surgery, Dr Hajjar and colleagues1 concluded that the use of a restrictive transfusion strategy (a hematocrit level less than 24% for red cell transfusion) was noninferior to a liberal strategy (a hematocrit level less than 30%) in terms of a combined outcome of 30-day all-cause mortality and morbidity among patients undergoing elective cardiac surgery. The authors' conclusion was based and dependent on a sample size estimated on an 8% noninferiority margin, ie, that the outcome of interest does not differ by more 8%.
Shehata N, Mazer CD, Thorpe KE. Blood Transfusion and Cardiac Surgery. JAMA. 2011;305(4):357-359. doi:10.1001/jama.2011.14