Advantages of Leukodepleted Concentrated Red Blood Corpuscles (Packed Cell)

Rupankar Sanyal *

RBC

Leukodepletion is the removal of white blood cells from a blood component. The leucocytes present in Concentrated Red Blood Corpuscles (Packed Cell) and Platelet Concentrate have been implicated in several important immunological and infective complications of blood transfusion. The blood filtration technology in the modern blood bank prevents these adverse effects. Prestorage filtration has significant advantages. There is strong clinical evidence that 3 log leukodepletion prevents or delays febrile reactions in patients receiving multiple red cell transfusions and can reduce cytomegalovirus transmission. Transfused leucocytes are the main agents for the 'immunosuppressive' changes in the recipient. Leucodepleted blood reduces the incidence of postoperative infection also.

The benefits of leukodepletion are as follows:

* Reduction in platelet refractoriness
* Reduction in FNHTR.
* Reduction in CMV risk.
* Reduction in TA-GVHD risk.
* Reduction in variant Creutzfeldt - Jakob disease (vCJD) risk.
* Chance of an organ transplant match is higher.
* Reduction in storage lesion effect.
* Reduction in transfusion related immunomodulatory effects, including cancer recurrence, mortality, and non-transfusion transmitted infection.

There are mainly four types of Leucoreduction:

1) Removing the Buffy coat from red cells at source.
This results in approximately a two log removal of leucocytes and may be sufficient to prevent most febrile nonhaemolytic transfusion reactions in patients who have previously experienced these reactions.

2) Filtering red cells and platelets.
Leukocyte depletion filters (LDF) effect a 3-4 log reduction of leucocytes when used correctly. Filtering is best accomplished at source as soon as possible after collection. It reduces the release of cytokines during storage.

3) Washing red cells.
This will achieve a 2 log removal, provided the Buffy coat is removed before or during the washing procedure. This product is generally not recommended as it is more expensive and less effective than LDF and the lifespan of the product is very short.

4). Freezing and deglycerolizing red cells.
The level of leukocyte depletion approximates that of LDF. This process is very expensive and is not recommended for the routine preparation of a leukocyte depleted product. Use of this product should be reserved for patients for whom long term storage is required either because they have a rare blood type or have multiple antibodies.

There are many different brands and types of LDF. Specific filters are designed for either red cell or platelet concentrate filtration.
It is always better to do leuco-filteration at source than bed side leuco-filteration. The following are the advantages of at source leuco-filteration:

1. It has been well established that filtration of blood and components at source results in more consistent. Filtration at source enables better control of most of the factor and quality assurance. Quality checks and comprehensive quality assurance programs can be more easily performed in the pre-storage setting.

2. Filtration at source, lower the incidence of febrile non-hemolytic transfusion reactions (FNHTR). FNHTR are caused not only by leukocyte antigen-antibody reactions but also by the cytokines produced by leucocytes in the transfused blood component. This would be more effectively prevented if the leucocytes were removed immediately after the blood is collected, avoiding the formation of cytokines. This is especially the case with platelet components stored at room temperature as it has been demonstrated that cytokine production occurs more rapidly at 20 °C than 4 °C.

3. Studies have documented a higher incidence of filtration failures when performed at the bedside as compared to leukocyte filtration performed in the laboratory setting.

4. Lower incidence of alloimmunization and diminished immunomodulation that may result from the transfusion of membrane fragments .Leukocyte degradation during storage results in cell fragments which may not be removed by post-storage filtration and these can provoke HLA or platelet alloimmunization. Moreover it is possible that leukocyte fragments released from cells harboring leucotrophic viruses and they may carry such viruses through the bed side filter.

5. Complications such as bradykinin-associated hypotension and transfusion related “red eye” syndrome have been reported with particular types of filters used at the bedside.

6. Early removals of leucocytes (within 24 hours) may reduce the likelihood of significant bacterial contamination of red cells, particularly relating to Yersinia enterocolica and coagulase-negative Staphylococcus

When bedside filtration is practiced, then it is somewhat safe to practice following

1) Stored blood for leukocyte filtration should be as fresh as possible.
2) Filter manufacturer's instructions for use should be strictly followed.
3) Blood should not be forced through the filter under pressure. Transfusion should take place as quickly as practicable under normal gravity.

Leukocyte filtration is a complicated process that is influenced by factors such as the blood component's prefiltration cellular composition and plasma content, the temperature of the blood component at the time of filtration, the filtration flow rate, the number of units transfused through the filter, and the timing of the filtration step.
Leukodepletion of blood components has become the international standard of practice. All advance country like USA, UK, Australia, the leukodepletion is mandatory nowadays.

In Shija Blood Bank & Transfusion Services, the leucoreduction is done by filtering red cells. (Buffy coat separation from red cell technique will be available within a month or two).

References: 1) Mollison's Blood Transfusion in Clinical Medicine.
2) Rossi's Principles of Transfusion Medicine.
3) Essential Guide to Blood Grouping Geoff Daniels, Imelda Bromilow
4) AABB
5) Reports of Australian Blood Bank Services