The Use of Fresh Plasma and a Plasma-free Medium to Enhance the Aggregation Response of Stored Platelets

Platelet aggregation in response to ADP (10 µM) and collagen (4 µg/ml) in fresh and stored platelet concentrates (PC) and the enhancement of aggregation of the stored platelets after resuspension in fresh plasma and plasma-free medium were measured. The ability of platelets in autologous plasma to respond to the two agonists decreased significantly on days 2 and 5 of storage to 18 and 4% (p < 0.001) respectively of that seen in platelet-rich plasma on day 0 (100%). A 2-fold or greater improvement (p < 0.01) in the aggregation response was achieved when the autologous plasma in stored PC was replaced by fresh allogeneic plasma just before testing. The effect was even greater (three-fold or more, p < 0.001) when the autologous plasma was first replaced by plasma-free medium followed by suitable dilution for the test in fresh allogeneic plasma. These observations indicate another way to rejuvenate stored platelets and enhance their residual capacity to aggregate ex vivo. They could provide a basis for a suitable test for use within a quality assurance programme for stored PC.