Stability of factors V and VIII in thawed fresh frozen plasma units.

Factors V and VIII, commonly regarded as unstable in unfrozen plasma, were assayed at various intervals up to 24 hours using plasma from 20 thawed fresh frozen plasma (FFP) units. Comparisons were made between units stored at 4 and 25 C. The mean factor V value did not significantly change during the postthaw test period. Mean factor VIII activity prior to freezing was 121 per cent, dropped to 89 per cent four hours after thawing, and gradually decreased to 67 per cent at 24 hours. There was no difference between those units stored at 4 C and those stored at 25 C after thawing; therefore, refrigeration does not appear necessary for factor V or VIII stability up to 24 hours after thawing.