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

Batroxobin-induced clots exhibit delayed and reduced platelet contractile force in some patients with clotting factor deficiencies

Thrombin causes platelet activation via multiple pathways, and deficient thrombin generation reduces platelet contractile force (PCF) during clot retraction. We hypothesized that PCF in blood samples from clotting factor-deficient patients would be diminished due to delayed or deficient thrombin generation. Blood samples from patients with fibrinogen, and factor V, VII, VIII, IX, X, XI and XIII deficiencies were compared to samples from normal controls. PCF in patient blood clotted with thrombin (1 NIH UmL(-1)) was compared to PCF in clots formed with batroxobin (0.25 micro g mL(-1)). PCF in the former should be normal, but PCF in the latter is dependent on thrombin generation within the sample and might be deficient. In factor VII-(n = 2, P < 0.05), factor VIII-(n = 6, P < 0.005) and factor XI-(n = 2, P < 0.05) deficient platelet-rich plasmas, PCF in batroxobin-induced clots was significantly lower than in thrombin-induced clots. In factor IX deficiency (n = 2), one patient had a dramatic reduction in PCF while a second patient had increased PCF. PCF was insignificantly (P = 0.346) reduced in two patients with factor X deficiency, and was normal in one patient with factor V deficiency. The factor X result is consistent with work in model systems, which indicates that as little as 1-3% factor X activity is sufficient to restore thrombin generation to normal. The factor V result probably indicates that the deficiency is incomplete. PCF in thrombin-induced clots was normal in all of these patients. Low fibrinogen and factor XIII deficiency reduced PCF in both thrombin- and batroxobin-induced clots. These results indicate that PCF is reduced, probably due to delayed thrombin generation, in some factor-deficient platelet-rich plasma samples.

Failure of the platelet-activating-factor antagonist WEB 2086 BS for treatment of chronic autoimmune thrombocytopenia

Thirteen patients with chronic autoimmune thrombocytopenia (AITP) were treated for 14 days with daily oral doses of 120 mg of the novel platelet-activating-factor (PAF) antagonist WEB 2086 BS. Clinical bleeding symptoms remained essentially unchanged in 9 patients and became more pronounced in the post-treatment period in 4 patients. In no case was an increase in platelet counts observed. While the PAF antagonist was well tolerated subjectively during treatment, most patients exhibited a prolongation of the sensitive "hemostasis time" (a modified bleeding time test) after treatment, but the Duke bleeding time was not changed. We conclude that the PAF antagonist WEB 2086 BS is ineffective for treatment of chronic AITP and should be used with caution in thrombocytopenic patients.