What are the recommended methods for leucodepletion (white blood cell reduction)?

Recommended Methods for Leucodepletion (White Blood Cell Reduction)

Prestorage leucodepletion is the recommended standard method for white blood cell reduction in blood products, as it provides more consistent quality control compared to bedside filtration.

Primary Methods of Leucodepletion

• Prestorage Filtration: The preferred method where leucodepletion occurs at the blood center before storage

  • Provides more consistent quality control 1
  • Results in residual leucocytes <5 x 10^6 per transfused unit 2
  • Eliminates the need for additional filtration at the time of transfusion 3
  • Has become routine in the United States and many other countries 1

• Bedside Filtration: Used in settings where prestorage leucodepletion is not implemented

  • Involves filtering blood components at the patient's bedside immediately before transfusion 1
  • Quality assurance is more challenging with this approach 1
  • May be less consistent in achieving target leucocyte reduction 2

Filtration Technology

• Integral Filter Systems: Modern systems incorporate filters directly into blood collection sets

  • Bottom and top (BAT) systems with integral filters can achieve >3.5 log leucodepletion 4
  • Most units processed this way contain <1 x 10^6 leucocytes 4

• Standard Leucodepletion Filters:

  • Modern generation filters can provide greater than 4 log reduction of WBCs 5
  • Should incorporate a 170–200 μm mesh filter when used with infusion devices 3
  • No additional special filters are needed when using allogeneic products due to prestorage leucodepletion 3

• Cell Salvage Considerations:

  • Leucodepletion filters should be considered during re-infusion of salvaged blood in cancer surgery 3
  • Also recommended when blood is salvaged from an infected surgical field 3
  • Evidence for leucodepletion filter use in obstetrics is mixed 3

Clinical Indications for Leucodepletion

• Primary Indications:

  • Patients with hematologic malignancies receiving chemotherapy, particularly those with acute myeloid leukemia (AML) 1
  • Patients with other types of leukemia and cancer patients receiving chemotherapy 3, 1
  • Transplant patients, especially allogeneic hematopoietic stem cell transplant recipients 6

• Benefits of Leucodepletion:

  • Reduces alloimmunization and platelet refractoriness 3, 1
  • Decreases febrile non-hemolytic transfusion reactions 1, 5
  • May reduce cytomegalovirus transmission 2
  • Can reduce postoperative infection rates 2

Important Considerations

• Leucodepletion via filtration can result in some platelet loss (up to 25-35%), potentially increasing the number of transfusion products required 1

• Both platelet and red blood cell products should be leukoreduced for optimal prevention of alloimmunization 6

• Leukoreduction should be implemented from the beginning of treatment for patients who will require multiple transfusions 6

• When using cell salvage, a 40-μm filter may be indicated if small bone fragments contaminate the surgical field 3

• For platelet transfusion, a clean 170–200 μm giving set should be used, as one previously used for red cells may cause platelets to stick to red cells and reduce effective platelet dose 3

Quality Assurance

• Effective leucodepletion should result in residual leucocytes <5 x 10^6 per transfused unit (99.9% or log 3 reduction) 2, 5

• Quality assurance remains an important challenge, particularly for bedside filtration 2

• Each hospital should have both a nominated clinical lead and a coordinator for cell salvage who oversee competence-based training and ongoing data collection 3