Is leucodepleted blood the same as using a leucoreduction (leuko) filter?

Leucodepleted Blood and Leukofilters: Understanding the Relationship

Leucodepleted blood and using a leukofilter are not the same thing, but rather leukofilters are one method used to achieve leucodepletion of blood products. Leucodepletion refers to the end result (blood with reduced white blood cell content), while leukofilters are a specific tool used to accomplish this reduction.

Relationship Between Leucodepletion and Leukofilters

• Leucodepletion is the process of removing white blood cells (leukocytes) from blood products to produce components with residual WBCs < 5 × 10^6 per unit (representing a 99.9% or log 3 reduction) 1
• Leukofilters are one of several methods to achieve leucodepletion, providing a relatively inexpensive and simple approach that maintains normal shelf life of the blood product 1
• Modern leukofilters can provide greater than 4 log reduction of white blood cells, with some newer filters achieving up to 5 log depletion 2

Methods of Leucodepletion

• Filtration using leukofilters (can be performed at bedside or prestorage) 3
• Apheresis machines that separate blood components during collection 4
• Other less common methods include washing of red cells, freezing and deglycerolisation (which yield products with only 24-hour shelf life) 1

Timing and Location of Leucodepletion

• Prestorage leucodepletion: Performed at the blood bank during blood collection and component preparation 5

  • Now the standard in the United States and many other countries 5
  • Provides more consistent quality control 3

• Bedside leucodepletion: Performed at the time of transfusion 5

  • May be used in countries where universal prestorage leucodepletion is not implemented 5
  • Quality assurance is more challenging with this approach 3

Clinical Effectiveness of Leucodepletion

• Different levels of leucodepletion may be required for different clinical purposes 6:

  • 1 log10 reduction may prevent febrile non-hemolytic transfusion reactions
  • 2 log10 reduction may prevent transmission of certain viruses
  • ≥3 log10 reduction may be necessary to prevent platelet alloimmunization

• The American Society of Clinical Oncology recommends leukoreduced blood products for patients with acute myeloid leukemia receiving induction chemotherapy, with high-quality evidence showing reduced alloimmunization and platelet refractoriness 7

Important Considerations

• Leucodepletion via filtration can result in some platelet loss (up to 25-35%) which may increase the number of transfusion products required 5
• There is no significant difference in factors V and VIII levels between plasma filtered by inline whole blood filters and apheresis machine, indicating both methods maintain satisfactory coagulation factor levels 4
• In a Japanese study, bedside leukoreduction showed lower frequency of immune-mediated platelet transfusion refractoriness (3.2%) compared to universal prestorage leukoreduction (7.3%), though this finding requires further investigation 5

In summary, leucodepleted blood is the end product with reduced white blood cell content, while leukofilters are one of the tools used to achieve this reduction. The choice between different leucodepletion methods depends on local resources, clinical needs, and blood banking practices.