Von Willebrand's disease: a comparative study of diagnostic tests

Standardization of the bleeding time

The Duke, Ivy and immersion methods for performing the bleeding time are reviewed and modifications of these methods are discussed. Certain of the automated devices are described. It is concluded that the bleeding time, when properly standardized, is an important test in the evaluation of a hemostatic disorder.

"Haemostasis time", a modified bleeding time test and its comparison with the Duke and Ivy/template bleeding times. II. Application in bleeding disorders

"Haemostasis time" (HT), the occlusion time of a Butterfly 25 short cannula inserted into the cubital vein, is a bleeding time modification comparable to the skin bleeding times according to Duke and Ivy/Mielke. It also measures platelet function and is not influenced more than the latter tests by clotting factors. In HT, subendothelium is replaced by a standard artificial surface. The technique was investigated in patients with haemophilia A and B, von Willebrand's disease (vWD), and defects of factors VII and XI. HT was prolonged in 9/16 patients with haemophilia A/B, but did not correlate with the factor VIII:C/IX:C values. However, it reflected the different bleeding tendencies in those patients as represented by early or late onset of bleeding symptoms and occurrence of spontaneous haemarthroses. Of the vWD patients, not classified by multimeric analysis, 15/31 had prolonged Simplate II bleeding times, 14/31 prolonged HTs. Only 20/31 patients had corresponding normal or prolonged bleeding times with both techniques. HT correlated significantly with the Duke bleeding time (p = 0.011), ristocetin cofactor activity (p = 0.003) and von Willebrand factor antigen (p = 0.022), while no correlations were found between these parameters and the Simplate II method. Statistical evaluation shows, that in vWD, HT can replace the less precise Duke bleeding time but not the non-related Ivy/Simplate techniques.

The factor VIII abnormality in severe von Willebrand's disease

We attempted to characterize the small amounts of factor VIII-related antigen detectable in the severe recessive form of von Willebrand's disease with newly developed radioimmunoprecipitin techniques and radiocrossed immunoelectrophoresis. Previous studies have failed to demonstrate factor VIII-related antigen in most patients tested even with the highly sensitive immunoradiometric assays. Using the newer techniques, we found antigen in the plasma of six of eight patients with severe von Willebrand's disease from different kindreds. Qualitative abnormalities of the trace quantities of factor VIII-related antigen were demonstrated in five of the patients, with absence or relative decrease of the larger, less anodal forms. In addition, five distinct patterns were observed, each suggesting a different molecular abnormality. Heterozygous parents had normal to moderately decreased factor VIII-related antigen, with normal crossed immunoelectrophoretic patterns. This study suggests that severe von Willebrand's disease is a heterogeneous syndrome with various underlying molecular defects.

Diagnosis of von Willebrand's disease. A comparative study of diagnostic tests on nine families with von Willebrand's disease and its differential diagnosis from hemophilia and thrombocytopathy

Nine probands with von Willebrand's disease, and their family members, totalling 43 people, were examined. Twenty-seven had a history of bleeding; 29 had an increased factor VIII activity:factor VIII related antigen ratio; 24 had a decreased factor VIII related antigen; 23 had a prolonged bleeding time; 19 had a reduced platelet adhesiveness; 16 had a decreased factor VIII activity; and 14 had an abnormal ristocetin-induced platelet aggregation. Eight members with both normal beleeding time and normal factor VIII activity were found to have other abnormal tests: elevated ratio of factor VIII activity to factor VIII related antigen in seven; decreased factor VIII related antigen in four; and reduced platelet adhesiveness in one. Therefore, ratio of factor VIII activity to factor VIII related antigen and factor VIII related antigen are more sensitive and may be used for the detection of heterozygous carriers of von Willebrand's disease. Although patients with thrombocytopathy may have a prolonged bleeding time, decreased platelet adhesiveness and reduced platelet aggregation by ristocetin, their factor VIII activity, factor VIII related antigen and ratio of factor VIII activity to factor VIII related antigen are normal and their abnormal ristocetin test cannot be corrected by the addition of factor VIII concentrate. Hemophilic subjects and hemophilic carriers, who are deficient in factor VIII activity, usually have a normal bleeding time, normal platelet adhesiveness, and normal ristocetin test. In contrast to patients with von Willebrand's disease, their factor VIII related antigen is normal or slightly increased and their ratio of factor VIII activity to factor VIII related antigen is significantly reduced. We conclude that ratio of factor VIII activity to factor VIII related antigen and factor VIII related antigen are not only more sensitive but also more specific for the diagnosis of von Willebrand's disease.