Venous thrombosis: prevalence and interaction of risk factors.

The key to understanding why certain individuals develop deep vein thrombosis at varying times, despite similar risk factors being present, is the realization of the importance of gene-gene and gene-environment interactions between risk factors. The discovery of factor V Leiden and several other coagulation abnormalities, which are now known to be common in the general population, has revolutionized the way in which the aetiology of venous thrombosis is viewed. On the basis of current knowledge, time-dependent models taking account of various forms of interaction have been developed.