Factor V Leiden - What does it mean for me?

What is my risk of a clot?

In the general population, the risk of having a blood clot (either a deep vein thrombosis or pulmonary embolus) is quoted at 1 in 2000 people each year. However, the risk is highly dependent on your age. If you are in your twenties the risk is about 1 in 10,000 and if you are over 70 years it is as high as 1 in 200. If you have the factor V Leiden mutation, your risk of developing a DVT or PE is 5 to 7 times higher than somebody without this condition.

In reality there is little benefit knowing the risk. Most people don’t know they have the Factor V Leiden mutation until they have had their first clot.

Only about 10% of people with Factor V Leiden will ever have a blood clot in their life. Most people with this condition do not know they have it.

What is my risk of a second clot?

Anybody who has had a blood clot is at risk of a second clot. If you have a blood clot after surgery, the risk of another clot is low at approximately 1% per year. However, if you have a blood clot for no obvious reason, the risk of a second clot is much higher up to 5% per year. Surprisingly, having factor V Leiden does not significantly increase your risk of a second event over the expected rate.

What treatment should I have?

You should receive exactly the same treatment as anybody else for an acute deep vein thrombosis or pulmonary embolus. Having factor V Leiden makes no difference to acute care. You should be started on a blood thinner as soon as your doctor suspects you have a blood clot and continue once the diagnosis is confirmed.

How long should I remain on treatment?

You should take a blood thinner for at least 3 months to treat a DVT or PE. You then have to make the difficult decision, should you stop treatment or stay on a blood thinner long-term? You should discuss this with your doctor.

The following need to be considered when deciding if long term treatment is needed.

What caused the blood clot? Was it provoked or did it occur for no reason?
Do you have a family history of clots?
Your age
Your gender.
Do you have other risk factors?
How serious was your first event?
What do you feel comfortable with?
Have you had a blood clot before?

In every case your doctor has to weigh up the benefit of staying on a blood thinner to prevent a clot, versus the risk of bleeding.

Case studies of imaginary patients

All patients in these scenarios have factor V Leiden. Click on each case to see if I would recommend long term treatment.

You are a 72 year-old man. One morning you wake with a painful swollen leg. Your doctor organises an ultrasound scan and confirms you have a DVT. You have not been unwell; nor been on a long flight; nor had any surgery recently. You have no other significant illness. Your sister had a DVT 5 years ago. You are given rivaroxaban for 3 months. Should you continue long term?

I would recommend you stay on treatment long term.
The risk of a second event is much higher in men than women. Additional risks in this case include the family history and the fact there is no obvious cause for the clot (unprovoked).
On balance continuing treatment is the safest option for you. You are comfortable with the plan to stay on treatment.

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You are a 93-year-old lady who fell over in the wind and fractured your hip. Two days after surgery for a hip replacement, you notice your leg is swollen. An ultrasound scan confirms a small below knee DVT. You had a stomach ulcer two years ago which bled and you needed a blood transfusion. You have never previously had a blood clot and you are not aware anybody else in your family has had a DVT or PE. You are given an anticoagulant for 3 months. Should you continue long term?

I would recommend you stop treatment after 3 months.
This was a provoked event so the risk of a second clot is low. The risk of bleeding gets higher as you get older and is increased if you have had a previous bleed. You do not have a family history of blood clots.
You have a low risk of a second clot but a very high risk of bleeding, It is safest for you to stop treatment as early as possible. You were happy to stop treatment.

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You are a 22-year-old woman who collapsed in the supermarket with chest pain and shortness of breath. You were rushed to hospital and found to have a massive pulmonary embolus on a CT scan. You were admitted to the intensive care unit for thrombolytic therapy (clot busting drug). You improved quickly and left hospital after a week. You had started the oral contraceptive 6 weeks prior to the collapse. You have no family history of blood clots. You are given an anticoagulant for 6 months. You are very nervous about stopping treatment. Should you continue long term?.

This is a provoked event due to the oral contraceptive. You are female and do not have a family history, therefore your risk of a second event is low if you avoid the oral contraceptive in future. However, this was a life-threatening episode, from the history you nearly died. In this case it is very important that your view on treatment is included in the assessment. On the basis of the medical history, you do not need long term treatment. However, as you are nervous about stopping and definitely do not want another similar clot, you would like to stay on treatment. The risk of bleeding is very low in somebody your age.
I would recommend you remain on long term treatment. This can always be reviewed in the future especially if you develop risk factors for bleeding.

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These cases are just examples to illustrate how doctors weigh up the various factors necessary to recommend treatment.

If you have the Factor V Leiden mutation and want advice about your treatment, you should talk to your own doctor.

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