Studies on the prolonged bleeding time in von Willebrand's disease.

Ten studies of the effect of cryoprecipitate infusion in four patients with von Willebrand's Disease (vWD) are reported. The doses studied (4, 8 and in one case 10 bags of cryoprecipitate) were based on previous reports of correction of the bleeding time (BT) with such doses. A modest shortening of the BT was observed in only 2 studies and complete correction of the BT at 1 and 4 hours was observed in only one study. This latter result could not be reproduced in a subsequent study of the same patient. In all cases, the von Willebrand factor antigen (vWF:Ag) multimer patterns were normal in the infused cryoprecipitate and in the recipients' plasma post infusion with the presence of high molecular weight multimers demonstrated in all samples. These results contradict earlier reports of the effect on the BT of similar doses of cryoprecipitate and suggest that the presence of the high molecular weight forms of vWF:Ag does not necessarily correlate with the presence of the factor which corrects the bleeding time.