ABSTRACT
It is now possible to identify hereditary risk factors in a substantial percentage
of patients presenting with a venous thrombotic event. Discovery of the factor V Leiden
and prothrombin G20210A mutations has greatly increased the percentage of patients
in whom venous thrombosis can be attributed to hereditary thrombophilia. There is
considerable uncertainty, however, as to how this information should be used in patient
management. Although prolonged anticoagulation at an international normalized ratio
(INR) of 2 to 3 is highly effective in preventing thrombotic recurrences, this benefit
is partially offset by the risk of major bleeding and the inconvenience associated
with oral vitamin K antagonists. Although low-intensity anticoagulation at a target
INR of 1.5 to 2 has recently been shown to be effective in preventing recurrent venous
thromboembolism after 3 to 6 months of treatment at an INR of 2 to 3, it has not been
demonstrated to reduce the risk of major bleeding complications. A decision as to
the overall benefit of extended anticoagulation therefore continues to require clinical
assessment of an individual patient's risk of recurrence in the absence of treatment
and the risk of bleeding at the chosen INR target range.
KEYWORDS
Thrombophilia - thromboembolism - anticoagulants - INR - factor V Leiden - prothrombin
G20210A mutation
REFERENCES
506 øGln mutation in the gene for factor V (factor V Leiden).
N Engl J Med.
1997;
336
399-403
kbauer@bidmc.harvard.edu
