Blood Clot FAQ's - Risk Factors For Blood Clots and Clotting Disorders

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The following is a list of risk factors for thrombosis and thrombophilia:

Q. What causes a Deep Vein Thrombosis or Pulmonary Embolism blood clot?

A. There are many known causes of clot formation. Prolonged bed rest or inactivity, such as a long plane ride, can cause reduced circulation in the legs, which provides the opportunity for clot formation. Major surgical procedures or physical trauma can also increase the risk.

Blood has several clotting factors, and an imbalance may lead to increased clot formation. There are genetic disorders known to contribute to clot formation. Pregnancy, oral contra-contraceptives, and hormone replacement therapy also increase the risk of clots.

Two-thirds of all clots have no identifiable cause, and this is the subject of ongoing research. Two risk factors recently discovered are Factor V Leiden and an elevated homo-cysteine level.

Thrombophilia

Q. What is Factor V Leiden?

A. Factor V Leiden is a hereditary condition present in 15-20% of PE/DVT patients of European ancestry. A positive test for Factor V Leiden increases the risk of clots about three to four times compared to someone without it. In general, this risk is still small.

However, if you are taking oral contraceptives and you have Factor V Leiden, the risk of a clot increases dramatically (about 35-fold). If you have Factor V Leiden, the risk of clots also increases with age.
For Factor V Leiden patients who stop anticoagulant therapy after treatment, the risk for a second clot is about three times greater than for those without it.

Q. If I have Factor V Leiden, should family members be tested for it?

A. If family members are considering taking oral contraceptives or becoming pregnant, they may wish to be tested. Recommendations for family testing remain controversial.

Q. What is homocysteine?

A. Homocysteine is a byproduct of protein metabolism that promotes clotting via an unknown mechanism.

An elevated homocysteine level is treatable with folic acid, B6, and B12. This condition (hyperhomocysteinernia) is much less common than the Factor V Leiden mutation.

Q. Is age a risk factor for clots?

A. Increasing age is a risk factor for DVT and PE.

Q. Is cancer a risk factor for clots?

A. Yes, although having a clot does not necessarily mean you have cancer.

Q. Is there an increased risk of blood clots to other family members since I've had a PE or DVT?

A. If you have tested positive for Factor V Leiden, family members may also have this condition and be at a slightly higher risk for clots.   Most clots are caused by non-genetic factors such as surgery, bed rest, cancer, pregnancy, etc., none of which would indicate that family members have an increased risk.