Background

In hospital practice, postmortem and other studies suggest that venous thromboembolism causes 10% of deaths and contributes to a further 15%. Although it is relatively less common in the community, where the prevalence varies with age between 1 in 10 000 and 1 in 1000 per year, it is still a major cause of concern. Anxiety runs highest when oral contraceptive or hormone replacement therapy is being considered, and a small number of women die each year from thrombosis associated with these agents. The importance of venous thrombosis is often considered largely in terms of risk of death, but this ignores considerable morbidity from the miserable and disabling postphlebitic syndrome, which will develop in >20% of survivors.

In most cases thrombosis arises from a combination of external circumstances and the inherited and acquired predisposition to thrombosis of an individual. Only 30-40% of cases seem to be completely spontaneous. So far we have been better at identifying high risk circumstances than high risk individuals, and so the concept of screening people for risk of thrombosis is relatively new. The tendency of some individuals to develop thrombosis more easily than others is often inherited, and the term thrombophilia has been coined to describe this condition. We can now identify a …