Factor V Leiden Mutation Analysis

The Factor V Leiden test checks your DNA for an inherited change in the F5 gene that makes blood more likely to clot. It is one of the most common inherited causes of thrombophilia, a tendency to form blood clots.

What the test looks for

Factor V is one of the proteins that help blood clot. Normally, another protein called activated protein C switches factor V off once a clot has done its job. The Factor V Leiden variant (G1691A in the F5 gene) makes factor V resistant to being switched off, so clotting can continue for longer than it should.

People can inherit:

• No copy of the variant
• One copy (heterozygous): the most common result in people who carry it; it raises the risk of clots modestly
• Two copies (homozygous): less common; it raises the risk more

Many people with Factor V Leiden never have a clot. The risk depends on other factors as well, such as surgery, long periods without moving, pregnancy, oestrogen-containing contraception or hormone therapy, other inherited clotting changes and family history.

The lab uses real-time PCR to detect the G1691A change in your DNA.

Who might consider it

A doctor may suggest this test if you have:

• Had a deep vein thrombosis (DVT) or pulmonary embolism, especially at a young age or without an obvious trigger
• Had a clot in an unusual place
• A close relative with Factor V Leiden or with repeated blood clots
• A history of certain pregnancy complications, as part of a wider clotting work-up

Some people with a strong family history ask about testing before starting oestrogen-containing contraception or hormone therapy. This is a decision to make with your doctor.

Before you book

The test uses one blood sample. Because it reads your DNA, the result is not affected by blood thinners or by having a clot at the time, unlike some clotting function tests. Our team can collect the sample at your home or office anywhere in Dubai, or you can visit our lab in Al Karama or Al Barsha 1. The lab asks for a signed consent form and your relevant medical history with the sample, as it does for all genetic tests. Results are usually ready in 3–5 days.

Factor V Leiden is often tested together with the prothrombin 20210 mutation and other thrombophilia tests, so ask your doctor whether a wider panel suits you better.

Understanding your results

• Not detected: you do not carry Factor V Leiden. This does not rule out other causes of clotting.
• Heterozygous (one copy): your risk of a blood clot is higher than average, but many people never have one.
• Homozygous (two copies): your risk is higher still, and your doctor will discuss how to reduce it.

A positive result does not mean you need treatment. Decisions about blood thinners, contraception, hormone therapy, pregnancy care or travel advice depend on your whole history, so always discuss the result with your doctor. Never start or stop a medicine because of this result alone.

Because Factor V Leiden is inherited, your parents, brothers, sisters and children may also carry it. Your doctor can advise whether they should be tested.