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Separation of the different blood constituents

Whole blood donations, which represent more than 80% of donations, are sent to the preparation department in order to undergo separation of their constituents and deleukocytation. Deleukocytation can be carried out at two different points in the process: either before the separation of the different blood cells or after the separation.

The timing of leukodepletion is very important, because it does not allow the same blood products to be produced. Indeed, if this deleukocytation is carried out before the separation, the platelets and leukocytes will be retained by the leukocytation filter. Thus, the blood donation will make it possible to produce a concentrate of red blood cells and a bag of plasma, but not a concentrate of platelets.


On the other hand, if leukodepletion is carried out after separation, platelets from whole blood donations will also be recovered to produce mixtures of platelet concentrates. The choice of leukodepletion time is determined when the whole blood donation is collected because the blood is collected in different devices depending on the leukodepletion time.

Separation of the different blood constituents

Blood is made up of red blood cells, platelets, leukocytes and plasma. The separation of the constituents makes it possible to reduce the risks for the recipient, by providing him only with the elements necessary for his recovery, thus avoiding the undesirable effects of the various products.

This separation can be carried out, either during a blood donation by automata (apheresis) which exclusively take the blood elements desired during the donation (plasma, platelets, red blood cells) and reinject the other constituents into the donor; or during a whole blood donation, faster than donation by apheresis, the constituents of which will be separated by the preparation department.


Whole blood is centrifuged to obtain the different layers of blood constituents (red blood cells, plasma and platelets if leukodepletion not performed before). After centrifugation, the bags of whole blood are pressed in order to keep only the red blood cells in the bag, at the bottom of the bag, and thus obtain Concentrated Red Blood Cells (CGR). The other constituents are collected in the other pockets of the collection kit to possibly produce mixtures of platelet concentrate (MCPS) and plasma.


The plasma thus recovered is frozen and the platelets will be mixed with 4 or 5 other donors from the same group in order to produce mixtures of platelet concentrates (MCPS).

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Leukodepletion of blood products

Whole blood bags are also deleucocyted (removal of white blood cells) either before separation with a filter that blocks the passage of white blood cells and platelets, or after separation by the press with a filter that only blocks leukocytes.

Deleukocytation allows the prevention of HLA allo-immunization (the presence of an anti-HLA leads to platelet transfusion inefficiency and reactions of chills/transfusion fever), the prevention of the transmission of intra-leukocyte viruses such as CMV , EBV, HTLV, prevention of bacterial risk (Yersinia enterocolitica) and prevention of the risk of transmission of Unconventional Pathogens (ATNC).

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Labeling and ABO Control

When the results of the biological qualification laboratories of the donation comply with the regulatory requirements, the CGRs are labeled and a final check is carried out after labeling in order to avoid any labeling errors. Non-compliant blood products will be labeled: "Unsuitable for transfusion".

Finally, the preparation department checks the ABO grouping of the bag from the tubing. This verification makes it possible to detect any errors in the qualification of the blood product, an error in the identification of the product (labeling problem, tube/bag inversion between two new donors), in order to reduce the immunological risk.

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