Pretransfusion Leukoreduction
The term "Pretransfusion Leukoreduction" is one that requires several definitions. Let's go in reverse order here and discuss "leukoreduction" first.
In the United States today, leukoreduction means running a blood product through a filter that is designed to remove the vast majority of the white cells in that product while retaining the vast majority of the other stuff that is in there. The filters most commonly used today are called "fourth-generation" filters, meaning not only that they contain the fourth wave of filter design technology, but that they are theoretically capable of removing 4 logs (or 99.99%) of white cells from a blood product.
"Pretransfusion", when used to describe the timing of leukoreduction, simply means at any time before the transfusion (but generally after the product has been stored). This procedure can be done at the patient's bedside (which used to be most common but is rarely done anymore) or in the Blood Bank prior to release of the product to the floor. Blood Bank Directors clearly prefer the procedure to be done in the transfusion service, because the process can be more carefully monitored and quality-tested.
Thinking back on the Red Cell Mechanism for FNH's, it would seem clear why pretransfusion leukoreduction might work (go ahead, check back on the mechanism. I'll wait right here...) Makes sense, right? If the reaction is caused by patient antibodies or other factors interacting with transfused white cells, removing the transfused white cells should prevent the reaction! In the vast majority of red cells transfusions, in fact, it does work. In platelet transfusions, though, this intervention just is not reliably effective. In fact, the failure of bedside or Blood Bank leukoreduction to reliably prevent FNH's in platelet transfusion was one of the observations which led those kooky researchers to discover the Platelet Mechanism for FNH's. Alas, more than pretransfusion leukoreduction was needed, and flying in to save the day is our next topic: Prestorage Leukoreduction.
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