Establishment And Clinical Application Of A Method To Evaluate Von Willebrand Factor Cleaving Protease Activity

Objective To establish a method for evaluating the activity of von willebrand factor cleaving protease(vWF-cp)and illustrated its clinical application.Method Purified von willebrand factor polymer which was used as enzyme substrate by gel filtration on Sepharose CL-4B of human fresh-frozen plasma. SWL method,which is the abbreviation of combinated sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE),immunoblotting (western blotting),and luminographic detection methods,was used to evaluate the vWF-cp activity of 60 healthy adults,27 patients with factorⅧdeficiency,28 patients with cerebal infarction,34 patients with liver cancer and 7 patients with thrombotic thrombocytopenic purpura(TTP)and the results were compared.Result The vWF-cp activity of 60 healthy adults and 96 patients were measured by this method.The sensibility of this method was 1.67%,its coefficient of variation(CV)intra- and inter- batch was 4.81%and 8.63 %respectively.The plasma vWF-cp activity was(86.53±17.49)%in health adults while it was(85.34±20.70)%in patients with factorⅧdeficiency which was approached that of healthy adults(p＞0.05).In patients with cerebal infarction,the plasma vWF-cp activity was(77.15±16.72)%which was lower than that of healthy adults(p＜0.05)and it was(67.88±12.96)%in patients with liver cancer which was significantly lower than that of healthy adults.For the patients with TYP,the vWF-cp activity was(9.06±7.17)%,significantly lower than that of healthy adults before plasma replacement(p＜0.01),then was higher in 24 hours after plasma replacement(47.00±6.27)%but still lower when compared to that of health adults(p＜0.01),it approached the level of healthy adults in convalescence stage(83.18±8.83)%(p＞0.05).Conclusion The von willebrand factor polymer which was used as enzyme substrate was purified by gel filtration on Sepharose CL-4B of human fresh-frozen plasma.The vWF-cp activity was measured accurately by SWL for healthy adults and patients with its good sensitivity,specificity and reproducibility and was suitable for clinical experiment.Tile vWF-cp activity was approached in patients with factorⅧdeficiency,lower in patients with cerebal infarction and more lower in patients with liver cancer and TTP when compared to that of healty adults. Plasma replacement could increase the vWF-cp activity effectively in patients with TTP.