Analysis of platelet factor 3 in platelet concentrates stored for transfusion

The amount of platelet factor 3 (PF3) activity expressed in stored platelet concentrates (PC) was measured in conjunction with extracellular LDH levels. Standard manual techniques for preparation of PC resulted in PF3 and LDH levels remarkably higher than those observed in PC prepared by apheresis or special manual plateletpheresis. During storage of PC, PF3 activity rose 2- to 10-fold, while LDH levels rose less than 2-fold over starting values. Loss of LDH and appearance of PF3 expressed as a percent of total per platelet were significantly correlated only in standard, manual PC. Approximately half of the PF3 activity observed in any type of PC remained in the supernatant plasma after centrifugation. Upon gel filtration, the supernatant PF3 activity eluted in a high molecular weight peak containing phosphate and light-scattering material. Our findings indicate that platelets in standard, citrated PC express PF3 in amounts that approach that of frozen-thawed (lysed) platelets; however, the manner in which the PF3 activity appears suggests that stored platelets undergo a combination of activation and damage processes.