Summary
The efficacy of five different factor VUI-von Willebrand factor (FVIII-VWF) preparations
in mediating adherence of blood platelets to damaged vessel walls was tested in an
annular perfusion chamber utilizing human arteries and reconstituted blood.
FVIII-VWF-purified by Sepharose CL-4B chromatography and von Willebrand factor prepared
from this preparation by dissociation with 0.25 M CaCl2 followed by Sepharose CL-6B chromatography were equally effective in mediating platelet
adherence as FVIII-VWF in cryoprecipitate and in plasma from normal subjects. A commercial
concentrate of FVIII-VWF (Hemofil, Hyland) used for the treatment of haemophiliacs
did not mediate platelet adherence at normal levels of FVIII-VWF related properties.
A recently developed high-purity FVIII-VWF preparation (Concentrate II) containing
multimers of high molecular weight normalized the platelet adherence. Platelet adherence
in plasma obtained from two patients with von Willebrand’s disease (VWD) was impaired,
but plasma samples obtained following treatment with Concentrate II mediated normal
platelet adherence. The normalization of platelet adherence paralleled the normalization
of the bleeding time.
This platelet adherence assay offers an inexpensive and efficient in vitro tool to test the efficacy of FVIII-VWF preparations designed for VWD patients. Preparations
such as cryoprecipitate and Concentrate II mediated the platelet adherence and normalized
the bleeding time. The commercial preparation did not mediate platelet adherence and
had no effect on the bleeding time.
Keywords
Platelet adherence - Bleeding time - Von Willebrand’s disease - FVIII-von Willebrand
factor