title: von Willebrand factor, clotting factors, and clotting inhibitors in apheresis platelet concentrates.
abstract: BACKGROUND
  Apheresis platelet concentrates (APCs) are usually stored in citrated plasma at 22°C. The stability of coagulation proteins-von Willebrand factor (vWF), 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.
  
  
  METHODS
  We measured CF activities and inhibitors in APCs on the day of manufacture (Day 0) and on Days 4, 5, and 7. vWF was determined by measuring vWF antigen (vWF:Ag) and vWF ristocetin cofactor (vWF: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). vWF:Ag increased during storage of APCs by 2% per day, with a relative loss of vWF:RCo and high-molecular-weight multimers.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Transfusion Medicine and Haemostaseology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: Dominik R
authors.initials: DR
authors.lastname: Weiss
authors.forename: D
authors.initials: D
authors.lastname: Franke
authors.forename: Erwin F
authors.initials: EF
authors.lastname: Strasser
authors.forename: Juergen
authors.initials: J
authors.lastname: Ringwald
authors.forename: Robert
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Reinhold
authors.initials: R
authors.lastname: Eckstein
mesh_terms: D001779:Blood Coagulation Factors / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D006801:Humans; D010983:Plateletpheresis; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D001779:Blood Coagulation Factors; D014841:von Willebrand Factor