In vitro and in vivo properties of various types of platelets.

The most popular procedures used to prepare platelet concentrates (PC) can be categorized into methods using platelet rich plasma (PRP) obtained by soft centrifugation of whole blood units, methods using buffy coats (BC) obtained by hard centrifugation of whole blood units, and apheresis procedures. The main feature that differentiates apheresis PC from whole blood unit derived PC is that apheresis reduces the number of donors necessary to support a recipient, although the advantages related to this feature have not been conclusively documented. From the biochemical point of view a limited number of comparative studies and a large series of non-comparative studies indicate that differences in PC obtained with different protocols depend more on the performance of the production laboratory rather than the preparative approach - PRP, BC or apheresis - itself. Similarly, the clinical effectiveness of PC seems to depend more on PC age, storage modalities and recipient's conditions rather than primarily on the method of PC preparation. Despite the basic differences in the three preparative approaches, all methods share a number of key elements that are necessary pre-requisites for a successful platelet transfusion therapy: minimization of the risk of bacterial contamination by careful donor skin disinfection and temperature control during PC production and storage; protection of aerobic metabolism during PC storage; laboratory quality control including at least pH and volume determinations, platelet and white cell counts and visual inspection of the swirling phenomenon at time of release. Future directions in the field of PC production include the development of new products such as infusible platelet membranes, thrombospheres, thromboerythrocytes and reconstituted freeze-dried platelets.