The Effect of Storage on the Expression of Platelet Membrane Phosphatidylserine and the Subsequent Impact on the Coagulant Function of Stored Platelets

BACKGROUND: Platelet concentrates (PCs) derived from whole blood and stored under standard blood bank conditions undergo changes that are referred to as the platelet storage lesion. This study assesses the effect of PC preparation and storage on the distribution of phosphatidylserine (PS) in the platelet membrane and the effect that this distribution may have on the thrombogenic potential of stored PCs.STUDY DESIGN AND METHODS: Fresh platelets and PCs donated by healthy donors were obtained. PCs derived from platelet-rich plasma were studied on Day 1, Day 3, and Day 6 of storage under blood bank conditions.RESULTS: Platelet aggregation after exposure to the platelet agonists ADP and epinephrine singly declined progressively, but, when ADP and epinephrine in combination and collagen and thrombin in combination were used as agonists, the decline in platelet aggregation was less marked. PS expression as measured by Annexin V binding (mean and SD) was 2.02 +/- 0.93 percent in fresh platelet samples and increased to 5.39 +/- 4.2 percent on Day 1, 22.1 +/- 7.1 percent on Day 3, and 39.5 +/- 12.1 percent on Day 6. Platelet prothrombinase activity (mean +/- SD) as measured by thrombin generation increased from 1.49 +/- 0.7 mu per mL in fresh platelet samples to 3.68 +/- 1.1 mu per mL in Day 1 platelets (p<0.001), 5.15 +/- 2.5 mu per mL in Day 3 platelets (p<0.001), and 4.65 +/- 2.48 mu per mL in Day 6 platelets (p<0.001).CONCLUSION: These results show that PS expression increases after preparation of PCs from platelet-rich plasma and rises progressively during platelet storage under blood bank conditions. Furthermore, the greater PS expression is associated with increased platelet-dependent thrombin-generating capacity.