STABILIZATION OF VONWILLEBRAND-FACTOR IN BANKED BLOOD BY LEUKOCYTE DEPLETION

The von Willebrand factor (vWf) activity as measured by the ristocetin co-factor (vWf: RCo) and collagen binding (vWf:CBA) assays, declined progressively in standard blood units stored at 4-degrees-C after a 2-day storage period. This loss of activity was accompanied by a loss and degradation of high molecular weight (HMW) vWf multimers. In studies using a paired design, filtration of blood with a high efficiency leucocyte-removal filter, prior to storage at 4-degrees-C, led to significantly improved maintenance of vWf:RCo and vWf:CBA compared with unfiltered units (P < 0.01 after 8 days). Loss and degradation of HMW vWf decreased when blood was filtered prior to 4-degrees-C storage. Filtration had no effect on vWf-associated activities when blood was stored at 22-degrees-C for 10 days. These results indicate that part of the storage lesion of vWf in banked blood is due to leucocyte-mediated removal and degradation of HMW vWf. This has implications when specifying plasma for the production of vWF concentrates and may also play a role in the haemostatic lesion associated with massive transfusion of stored blood.