v on W illebrand factor, clotting factors, and clotting inhibitors in apheresis platelet concentrates

Background Apheresis platelet concentrates ( APCs ) are usually stored in citrated plasma at 22°C. The stability of coagulation proteins— v on W illebrand factor (v WF ), clotting factors ( CFs ), and their inhibitors—has often been described in association with the storage of thawed plasma. However, fewer data are available regarding changes in APCs . Study Design and Methods We measured CF activities and inhibitors in APCs on the day of manufacture ( D ay 0) and on D ays 4, 5, and 7. v WF was determined by measuring vWF antigen (v WF : A g) and vWF ristocetin cofactor (v WF : RCo ) and by multimer analysis. Results Twenty‐one PCs obtained by plateletpheresis were studied. Major changes were observed for Factor ( F ) VIII (37% loss of activity within 4 days), FV (20% within 4 days), and protein S (76% within 4 days). All other CF activities remained higher than 80% over the 7 days. Fibrinogen and the inhibitors antithrombin and protein C remained quite stable. FXI , FXII , and FXIII actually increased during storage (8, 11, and 12% within 4 days). v WF : Ag increased during storage of APCs by 2% per day, with a relative loss of v WF : RCo and high‐molecular‐weight multimers. Conclusion Even after 7 days of storage at 22°C, the hemostatic potential of the plasma content in APCs was roughly preserved. The increase in FXII antigen indicates that this CF may also be stored in platelets; however, this has not yet been described.