What Are Leukocyte-Reduced Red Blood Cells for Transfusion?
Leukocyte-reduced red blood cells are RBC units that have had the majority of contaminating donor white blood cells removed through filtration, reducing leukocyte content to less than 5 × 10⁶ cells per unit, primarily to prevent alloimmunization, febrile transfusion reactions, and CMV transmission.
Definition and Processing
Leukocyte-reduced (leukodepleted) RBCs are manufactured by removing white blood cells through specialized filtration systems that achieve a 3-4 log reduction in leukocyte contamination 1. This process can be performed at two different time points:
- Prestorage leukoreduction: Removal of leukocytes immediately after blood collection, before storage or fractionation
- Poststorage leukoreduction: Filtration performed after storage, either at the blood bank or bedside
Prestorage leukoreduction is superior because it prevents the accumulation of cytokines that leukocytes release into plasma during storage, which are responsible for most febrile transfusion reactions 1.
Clinical Benefits
The evidence demonstrates multiple advantages of leukoreduction:
Prevention of Alloimmunization
The landmark TRAP trial (603 patients with newly diagnosed AML) showed that leukoreduced RBCs and platelets reduced lymphocytotoxic antibody formation from 45% in controls to 17-21% in leukoreduced groups 1. This translates to a reduction in immune-mediated platelet refractoriness from 13% to 3-5% 1.
Reduction of Transfusion Reactions
Leukoreduction substantially decreases febrile nonhemolytic transfusion reactions, which are primarily caused by cytokines elaborated by leukocytes during storage 1. The rate drops from approximately 2.15% with poststorage leukoreduction to 1.1% with prestorage leukoreduction 2.
Prevention of CMV Transmission
Leukoreduced blood components are equally effective as CMV-seronegative blood in preventing transfusion-transmitted CMV infection 1, 3, 4.
Current Practice Standards
In the United States and several other countries, the overwhelming majority of blood products are now leukoreduced at the time of blood collection and component preparation 5. This universal prestorage leukoreduction has become standard practice, eliminating the need for additional filtration at transfusion 5.
Specific Indications
Strong Evidence for Use:
- Patients with AML receiving induction chemotherapy - Level I evidence supports leukoreduction of both RBCs and platelets from diagnosis 1, 5
- Patients requiring long-term transfusion support - Those expected to need multiple transfusions throughout their treatment course 1
- Patients with other leukemias and cancers receiving chemotherapy - Though randomized trials focused on AML, benefits likely extend to these populations 5
Limited Indication:
- Short-term transfusion needs - Not cost-effective for patients undergoing high-dose chemotherapy with stem-cell transplantation who typically require only a few transfusions 1
Important Caveats
Platelet loss can be substantial - Filtration may result in 25-35% platelet loss, potentially increasing the number of transfusion products required 1. This is less of a concern with modern apheresis techniques that achieve leukocyte contamination below 5 × 10⁶ without additional filtration 1.
Timing matters for maximum benefit - The TRAP study showed that alloimmunization often develops after 3-4 weeks of transfusion 1. Therefore, the major clinical impact is seen in patients receiving intensive consolidation therapy, not just induction. Only 10-15% of AML patients may actually benefit clinically from alloimmunization prevention 1.
Storage and Administration
Leukoreduced RBCs are stored at 4 ± 2°C with a maximum shelf-life of 28 days (35 days with adenine) 6. Transfusion should be completed within 4 hours using a 170-200μm filter 6.