Ferraris and colleagues have published an analysis of data from the American College of Surgeons’ National Surgical Quality Improvement Program that includes 941,496 patients. They found that blood given introperatively was harmful and the risk rose with each unit of blood given. It is unlikely that differences between patients who were transfused and those not transfused were adequately adjusted for despite the use of propensity scores. Thus, this paper shows once again that patients who are transfused are sicker than patients not transfused, NOT that blood is harmful. Only a randomized clinical trial can provide unbiased assessment of risk and benefit of blood transfusion.

– Jeffrey L. Carson