Factor V Leiden Mutation
and PT 20210 Mutation

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Also known as: Activated protein C resistance; APC resistance; Factor V R506Q; PT G20210A; Factor II 20210
Formal name: Factor V Leiden mutation; Prothrombin 20210 mutation
Related tests: Antithrombin; Protein C and Protein S; Homocysteine; MTHFR Mutation; Factor V R2 A4070G Mutation

At a Glance

Why Get Tested?

To determine whether you have an inherited gene mutation that increases your risk of developing deep venous thrombosis (DVT) and/or venous thromboembolism (VTE)

When to Get Tested?

When you have had an unexplained blood clot (thrombotic episode), especially when you are less than 50 years old, have recurrent DVT/VTE episodes, or have a strong family history of thrombosis.

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Factor V and prothrombin are coagulation factors, two of a group of proteins produced by the liver that are essential for proper blood clot formation. When a body tissue or blood vessel wall is injured, a process called hemostasis begins to form a plug at the injury site to help stop the bleeding. Cell fragments called platelets adhere to and aggregate at the injury site, and a coagulation cascade is initiated to sequentially activate coagulation factors. As the process progresses, thrombin converts fibrinogen into fibrin threads that crosslink to form a fibrin net. The fibrin net adheres to the injury site along with the platelets and forms a stable blood clot. This barrier prevents additional blood loss and remains in place until the injured area has healed.

There must be an adequate number of platelets and each of the coagulation factors and each must function normally in order for a stable blood clot to form and then dissolve when no longer needed. Too little, dysfunctional, or too much of the factors can lead to bleeding or thrombosis.

Factor V Leiden and prothrombin 20210 are produced by genetic mutations that lead to the production of altered factor V protein and increased amount of prothrombin protein, respectively. They are associated with an increased risk of inappropriate clotting (thrombosis). They are independent mutations that are tested separately, but the tests are often performed at the same time as part of the investigation of a thrombotic episode in someone who is suspected of having an inherited risk factor for a clotting (hypercoagulable) disorder. The testing of each is intended to identify whether or not the specific mutation is present and to determine whether the person has one (heterozygous) or two (homozygous) copies of that mutation.

Factor V Leiden is a variant form of factor V associated with a genetic point mutation. The altered protein produced as a result of this mutation activates normally during clotting, but it resists being degraded by activated protein C (APC) during coagulation. APC helps to regulate and slow coagulation as a balance check. Resistance to its actions leads to prolonged factor V activity and thus to an increased risk of venous thrombosis and venous thromboembolism (VTE).

Factor V Leiden mutation is the most common inherited predisposition to abnormal clotting in the United States. Its prevalence is about 5% of the Caucasian population. A person with a factor V Leiden mutation may be heterozygous or, more rarely, homozygous. Those who are heterozygous have a 3 to 8 fold greater risk of developing a VTE than those who don't carry the mutation, while those who are homozygous have a 50 to 80 fold increased risk of thrombosis.

Prothrombin (PT) 20210 is a variant form of prothrombin gene, also caused by a genetic point mutation. PT 20210 is also associated with an increased risk of VTE.

Someone with a PT 20210 mutation may be heterozygous or homozygous, although it is very rare to find individuals who are homozygous. The affected heterozygous person will have a mild to moderate increase in their thrombin production, which is associated with 2.5 to 3 fold greater risk of developing a VTE; there is not enough information about risk in those who are homozygous. Although PT 20210 is less common in the U.S. than factor V Leiden (about 1-2% of the general population), it is also more prevalent in Caucasians than in those of other ethnic backgrounds.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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