Factor V Leiden Mutation and PT 20210 Mutation

Other names: Factor V R506Q; Factor V Leiden mutation: Activated protein C (APC) resistance; factor II 2021; Prothrombin 20210 mutation: PT G20210A

Factor V and prothrombin are coagulation factors, which are proteins that are involved in the coagulation (clotting) of the blood. The factors are involved in a procedure called the coagulation cascade, which takes place in a series of stages when the body starts to bleed. Factor V Leiden is a variation of Factor V; it has a genetic point mutation, which means the nucleotide is different on the gene which controls Factor V production. The mutation does not prevent the protein from being activated in the coagulation cascade but it does affect the degradation process, which causes there to be a higher degree of thrombin in the blood than normal; this can increase the risk of a patient developing a venous thromboembolism.

Why is the test used?

The test is primarily used to diagnose the cause of venous thromboembolism; it is usually ordered after patients have had a thrombotic episode. The test is usually done if a patient has had a thrombotic episode in a strange place (for example in the liver, brain or the kidneys), the patient has never had a thrombotic episode before or the patient is under the age of 50.

The test may also be used when a patient has history of thromboembolisms in their family; tests may also be ordered for pregnant women, women who are on the oral contraceptive pill and women taking hormone replacement therapy if they have a thrombotic episode.

How is the test done?

The test is performed by the insertion of a needle into an arm vein (usually on the inside of the elbow) and collecting the blood in a syringe. Once the doctor has a sufficient sample, the blood will be placed in a bottle, labelled with the patient’s name and sent away to the laboratory for analysis.

What do the test results mean?

If the test shows that the patient is resistant to activated protein C, this is usually caused by Factor V Leiden. Further genetic testing will be ordered to confirm the mutation.

Genetic testing may show that the individual has one or two copies of the mutated gene; this means they are either heterozygous (one copy) or homozygous (two copies). The severity of the condition will vary between individuals and some people may never develop a VTE even though they have Factor V Leiden.

Specific Blood Tests

Blood Test Guide

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