Preparation

Whole blood donation
For a whole blood donation, about 500 ml of blood are taken from the donor in 70 ml of anticoagulants (consisting of citrate-phosphate-dextrose [CPD]) and immediately cooled to about 22 oC. Within 24 hours of extraction, the blood is separated through centrifugation into erythrocytes, a buffy coat (the intermediate layer between erythrocytes and plasma in which the majority of the leukocytes and thrombocytes find themselves) and plasma. The erythrocytes are suspended in storage fluid and filtered over a leukocyte-removing filter shortly after the preparation. The thrombocytes are isolated from one or more buffy coats. The leukocytes are also removed from here through filtration. The plasma is frozen, and forms the raw material for the preparation of medicines from human plasma.

Aphaeresis
The blood can be divided into different components during the extraction with an aphaeresis machine. In this way, a specific part (such as plasma or thrombocyte concentrate) can be extracted while the other blood components (for example, erythrocytes) can be given back to the donor. This method enables the harvesting of a relatively large amount of one component from one donation. The leukocytes can be removed from the blood components with a filter or through a procedure on the aphaeresis machine. Sodium citrate (which contains no dextrose) is normally used as the anticoagulant for plasmaphaeresis. ACD-A (which does indeed contain dextrose) is used as the anticoagulant for thrombocyte aphaeresis.
Plasma obtained through aphaeresis is frozen after extraction. After the ABO and Rhesus (D) blood group assays, and the currently applicable tests for infections diseases allow for release of the transfusions, the product is put in quarantine until the donor is tested once again after an interval of a minimum of 6 months and found to be negative in the tests then applicable. This method strongly reduces the ‘residual risk’ of the transmission of viruses through so-called ‘window donations’.

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Bacterial contamination
Blood products can be contaminated with bacteria. Bacteria can either enter the donor blood through injection for the blood donation (skin bacteria), or because the donor has a (sub-clinical) bacteraemia. Because thrombocyte products are stored at room temperature (20 - 24 °C), the risk of the growth of bacteria in this product is relatively greater than in erythrocytes that are stored at 2 – 6 °C.
Therefore, all thrombocyte products are put into culture in an aerobic or anaerobic medium and incubated in an automated system immediately after preparation. This screening is considered positive with the development of CO2, and this means that both the thrombocytes as well as the erythrocytes that were prepared from this donation may not be released. The culture report is checked before the release of thrombocytes, and the thrombocytes are released as ‘negative to date’. The culture is then continued to 7 days.
If the culture is positive after the release of the thrombocytes or the erythrocytes, then you will be informed of this so that transfusions can still be prevented. If the blood products have already been transfused, then the clinical course of the transfusion is decisive for the policy. When culturing thrombocytes from 5 donations, 0.5 to 1% provides a positive result.

Leukocyte removal
Leukocytes in erythrocyte products and thrombocyte products can be the cause of, among others, fever reactions after transfusion, allo-immunisation by HLA-antigen, transmission of viruses, immune modulation, and Graft versus Host Disease. Leukocytes are removed from erythrocyte and thrombocyte products through filtration. This results in the number of leukocytes in the product being reduced to < 1 x 106 per product. There are data that point to the fact that leukocyte removal from the cellular blood products provides a health gain for all patient groups and improves the quality of the product (Health Council Report).
As from 1 January 2002, the only cellular products still delivered were those in which the leukocytes had been removed.
Blood products in which the leukocytes have been reduced to less than 1 x 106 are, as previously, considered to be CMV-free. The degree of CMV safety is equivalent to the testing of donors for the presence of anti-CMV antibodies.
The number of leukocytes in plasma will also be reduced to < 1 x 106 per product. This plasma will be delivered as of 1 July 2003.

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