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9.4.3.3 Platelet concentrate
Platelet concentrates are derived from whole blood or are obtained by apheresis.
After collection, whole blood can be kept for up to 24 hours in conditions that are consistent with the preparation of plasma see section 9.4.3.4. and
validated to maintain a temperature between 20°C and 24°C, following international or NRA recommendations. The whole blood unit is centrifuged
so that an optimal number of platelets remain in plasma platelet-rich plasma, or PRP. Platelet concentrates are then obtained by hard-spin
centrifugation of PRP and are then resuspended.
However, if whole blood is centrifuged so that the blood platelets are primarily sedimented to the buffy coat layer, the buffy coat is separated and further
processed to obtain a platelet concentrate. Either a single buffy coat or a pool of buffy coats is diluted with plasma or an appropriate nutrient solution, and
platelets are concentrated by further centrifugation. The platelet content per unit depends on the method of preparation. Similarly, the residual leukocyte
content will vary according to the centrifugation parameters.
Platelet concentrates both from whole blood and apheresis should be stored in conditions that guarantee that viability and haemostatic activities
are optimally preserved. The storage temperature should be 20–24°C. Continuous gentle agitation of platelets during storage should be suffi cient
to guarantee the availability of oxygen to the platelets but should be as gentle as possible. A storage time should be defi ned in accordance with
national regulations set by the NRA; it should normally not exceed fi ve days in the absence of additional measures.
In special circumstances, volume-reduced, split, washed or irradiated platelet concentrates can be prepared for specifi c treatments.
Periodic quality control should be performed on the fi nal product to ensure that the manufacturing process is consistent see 9.6. At a minimum, the
following critical parameters should be checked during the quality control assays:
— volume; — platelet content;
— residual leukocytes, if leukocyte reduction is performed; — pH, measured at the end of the recommended shelf-life.
9.4.3.4 Plasma for transfusion and Plasma for fractionation
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