Leukoreduction vs buffy-coat depletion and the safety of blood transfusion.

Abstract

To the Editor: Dr Hebert and colleagues found that a national universal leukoreduction program for red blood cell (RBC) transfusion reduced the rates of mortality and morbidity after RBC transfusions in high-risk patients. Although the authors state that RBCs transfused in the period before the introduction of the policy were stored in an additive solution, they do not indicate whether any of these units underwent depletion of the buffy coat. It also would be important to know about clinical use of microaggregate filters at the bedside. Furthermore, RBCs that are not leukoreduced by filtration may vary in their risk of transfusion reactions. Buffy coat– depleted units contain about 70% fewer white blood cells and fewer microaggregates than does blood that has not been depleted of the buffy coat. Blood that is neither filtered nor depleted of the buffy coat, but which is transfused through a microaggregate filter, will contain fewer platelet and white blood cell aggregates than blood not so transfused. If a substantial number of transfusions before the policy were of buffy coat–depleted RBCs, then comparison of outcome between those receiving either leukoreplete RBCs or buffy coat– depleted RBCs before introduction of the policy with those patients transfused after introduction of the policy might strengthen the findings in favour of leukoreduction, either by filtration or by depletion of the buffy coat. Alternatively, if very few patients received buffy-coat depleted RBCs before the policy, then the findings do not exclude an equally beneficial effect from depletion of the buffy coat, a less expensive procedure than leukoreduction by filtration. Most European studies have compared buffy coat–depleted RBCs with RBCs that have been leukoreduced by filtration, with conflicting results. We reported a trial in patients undergoing cardiac surgery, comparing nonleukoreduced blood, buffy coat–depleted RBCs, and RBCs leukodepleted by filtration. The study did not have enough power to assess mortality, but the findings with regard to infection were essentially negative. There was a trend, however, toward higher rates of infection in the group that received nonleukoreduced blood, with equal rates of infection in the other 2 groups. Thus, without more information on the RBC product used before the policy began, it should not be assumed from the study of Hebert et al that leukoreduction by filtration is the only option for reducing the postulated adverse effects of passenger leukocytes.