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Factor V antigen levels and venous thrombosis: Risk profile, interaction with factor V leiden, and relation with factor VII antigen levels

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Author: Kamphuisen, P.W. · Rosendaal, F.R. · Eikenboom, J.C.J. · Bos, R. · Bertina, R.M.
Institution: Gaubius Instituut TNO
Source:Arteriosclerosis, Thrombosis, and Vascular Biology, 5, 20, 1382-1386
Identifier: 235536
Keywords: Adolescent · Adult · Aged · Drug Resistance · Factor V · Factor VIII · Female · Humans · Male · Middle Aged · Protein C · Risk Factors · Venous Thrombosis


Clotting factor V has a dual function in coagulation: after activation, procoagulant factor V stimulates the formation of thrombin, whereas anticoagulant factor V acts as a cofactor for activated protein C (APC) in the degradation of factor VIII/VIIIa, thereby reducing thrombin formation. In the present study, we evaluated whether plasma factor V levels, either decreased or increased, are associated with venous thrombosis. High procoagulant factor V levels may enhance prothrombinase activity and increase the thrombosis risk. Low anticoagulant factor V levels could reduce APC- cofactor activity in the factor VIII inactivation (APC-resistant phenotype), which might also promote thrombosis. Low factor V levels in combination with factor V Leiden could lead to a more severe APC-resistant phenotype (pseudohomozygous APC resistance). To address these issues, we have measured factor V antigen (factor V:Ag) levels in 474 patients with thrombosis and 474 control subjects that were part of the Leiden Thrombophilia Study (LETS). Factor V:Ag levels increased by 7.6 U/dL for every successive 10 years of age. Mean factor V:Ag levels were 134 (range 41 to 305) U/dL in patients and 132 (range 47 to 302) U/dL in controls. Neither high nor low factor V:Ag levels were associated with venous thrombosis. We found that factor V:Ag and factor VIII antigen levels in plasma were correlated, but factor V did not modify the thrombotic risk of high factor VIII levels. The normalized APC ratio was not influenced by the factor V:Ag level in subjects with or without factor V Leiden. We conclude that neither low nor high factor V:Ag levels are associated with venous thrombosis and that factor V:Ag levels do not mediate the thrombotic risk associated with high factor VIII levels. Chemicals/CAS: factor V Leiden; Factor V, 9001-24-5; Factor VIII, 9001-27-8; Protein C