Simple screening tests for the diagnosis of isolated clotting factor defects. With special reference to 'contact factor' defects

Multiple cerebral thrombosis in Fletcher factor (prekallikrein) deficiency: a case report

Despite markedly prolonged activated partial thromboplastin times (APTT) patients with Fletcher factor (prekallikrein) deficiency do not clinically bleed. However, there is one reported case of myocardial infarction associated with prekallikrein deficiency. These clinical observations suggest that the contact mechanism has a minor role in normal in vivo hemostatic function. We report a further two cases of prekallikrein deficiency in Caucasian siblings. The propositus presented with multiple cerebral thrombosis. Cautious anticoagulation resulted in massive cerebral hemorrhage and death of this patient. The sibling was investigated in an attempt to establish a possible defective fibrinolytic pathway in vivo. New sensitive tests for fibrinolysis were used. These included radioimmunoassay of fibrin degradation product "D," B beta 15-42, and in vitro 125I-labelled fibrin lysis assays. The plasma half-life of prekallikrein in this patient was calculated to be 58 hr. Family studies of heterozygotes were also performed. Prekallikrein deficiency is found not to be important in normal in vivo fibrinolysis, which possibly operates via tissue or vessel wall fibrinolytic activator release.

An approach to the evaluation of hemostasis

Effective hemostasis may be adequately and quickly evaluated using tests that are readily available in the usual hospital laboratory. This evaluation includes peripheral smear for platelet morphology and number, platelet count, bleeding time, activated partial thromboplastin time (aPTT), prothrombin time (PT), and clot retraction. Normal results of these tests exclude all but the mildest disturbances of hemostasis.