Study of factor XII (Hageman factor) in some cases of thrombosis

46 patients suffering from arterial and venous thromboembolism and 10 healthy subjects were tested for Hageman factor (F.XII) coagulant activity. The patients were divided into 5 subgroups according to the type of thrombotic complication. Among patients with exclusively recurrent venous thromboembolism only one of 8 patients was deficient in F.XII. Among patients suffering from recurrent myocardial infarction the incidence of F.XII deficiency was significantly higher (20%, P <0.05). Among patients with unstable angina, only one of 10 patients had factor XII deficiency. Among patients suffering from recent or old myocardial infarction, the incidence of F.XII deficiency was not significant. Thus the reduced levels of F.XII should be considered as a risk factor in the development of thromboembolism.