Elevated clotting factor levels and venous thrombosis.

Increased plasma levels of fibrinogen, factor VIII (FVIII), factor IX (FIX), factor XI (FXI) and prothrombin all were reported to be independent risk factors of venous thromboembolism (VTE). However there is only limited information on the molecular basis of these plasma phenotypes. In addition some of these plasma phenotypes may form clusters, which may point to defects in common pathways affecting biosynthesis or clearance. Uncertainties as to what should be considered the cut-off for an elevated plasma level and in some cases (FIX, FXI) the lack of published confirmatory and/or prospective studies, have delayed the incorporation of these parameters in thrombophilia screening procedures.