LabCorp and its Specialty Testing Group, a fully integrated portfolio of specialty and esoteric testing laboratories.
To determine whether you have an inherited gene mutation that increases your risk of developing a blood clot, including a deep venous thrombosis (DVT) and/or venous thromboembolism (VTE)
When you have had an unexplained blood clot (thrombotic episode), especially when you are less than 50 years old, have recurrent DVT or VTE episodes, experienced DVT or VTE during pregnancy, had DVT at unusual sites, or have a strong family history of thrombosis
A blood sample drawn from a vein in your arm
Factor V Leiden and prothrombin 20210 (PT 20210 or Factor II mutation) are genetic mutations that are associated with an increased risk of developing inappropriate blood clots. These mutations are tested by two separate tests that evaluate a person's DNA to look for the mutations. The two tests are often performed together to help determine if an individual has an inherited risk for excessive clotting.
Factor V and prothrombin are coagulation factors (sometimes called clotting factors), two of a group of proteins essential for proper blood clot formation. When an injury occurs and bleeding starts, a process called hemostasis begins to form a plug at the injury site to help stop the bleeding. Blood cells called platelets adhere to and aggregate at the injury site, and a coagulation cascade begins to activate coagulation factors in sequence. Eventually, a blood clot forms. Once the area has healed, the blood clot dissolves.
There must be an adequate number of 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. A deficiency in clotting factors (quantitative defect) or clotting factors that do not work properly (qualitative defect) can lead to excessive bleeding or clotting (thrombosis).
Factor V Leiden and PT 20210 are two mutations that individuals may inherit from their parents that may cause an increased risk of excessive clotting. They are inherited in an autosomal dominant manner. A person may inherit one mutated gene copy and be heterozygous or may inherit two mutated gene copies and be homozygous. This may determine to what extent the person is affected. (For additional details, read the section on Autosomal Dominant Inheritance in the Genetic Disorders article.)
These two mutations are independent and are tested separately, but the tests are often performed at the same time as part of the investigation of a blood clot (thrombotic episode) in someone who is suspected of having an inherited risk factor for an excessive clotting (hypercoagulable) disorder. Each test is used to identify whether or not the specific mutation is present and to determine whether the person has one copy (heterozygous) or two copies (homozygous) of that mutation.
Factor V Leiden (FVL) mutation and prothrombin 20210 (PT 20210) mutation tests are two tests often used together to help diagnose the cause of inappropriate blood clot (thrombus) formation, including deep vein thrombosis (DVT) and/or venous thromboembolism (VTE).
Testing for factor V Leiden and PT 20120 mutations is used to help determine if an individual has inherited a disorder associated with blood clots and can determine whether the person has one copy or two copies of the mutation (heterozygous or homozygous.)
These tests may be ordered to help determine the reason for an initial harmful blood clot (thrombotic episode), especially when it occurs in a person under 50 years old, is unprovoked, or is in an unusual place such as the liver (hepatic), the kidneys (renal), the brain (cerebral), the gut and pelvis (mesenteric), or in the eye veins. These tests may also be ordered if VTE is recurrent or there is a strong family history of thrombosis.
Experts do not recommend screening the general population and are divided on testing family members of those with a factor V Leiden or PT 20210 mutation. If the mutation is present, then the person is at a higher risk for developing a blood clot, but there is variability in how the gene is actually expressed. With factor V Leiden, for example, only 10% of those with the factor V Leiden mutation will ever have a thrombotic episode.
Factor V Leiden mutation and PT 20210 tests are ordered when it is suspected that a person has an inherited risk factor for blood clots, for example, when an individual:
These tests may be ordered when a first-degree family member, such as parent or sibling, has a factor V Leiden or PT 20210 gene mutation. However, a panel assembled by the Centers for Disease Control and Prevention to evaluate practical genomics recommended in 2011 that if the goal is to decide on treatment with anticoagulant medication, adults without VTE symptoms do not need to be tested even if their family members have the PT 20210 or the factor V Leiden mutation.
If asymptomatic family members know that they have one or more of the mutations, they may be motivated to address controllable clotting risk factors such as oral contraceptive use, smoking, and elevated levels of homocysteine and be more aware of the potential risks of factor(s) triggering events, such as immobilization and surgery. However, many of those with the mutation will never experience a DVT or VTE.
If genetic testing indicates that an individual has one factor V Leiden or PT 20210 gene copy, then the person is heterozygous; if there are two copies, then the person is homozygous for the mutation.
The risk of excessive clotting from these mutation(s) varies from person to person. If you are asymptomatic, you may never have a DVT and/or VTE. If you have had one or more blood clots, then the mutation(s) is the most likely cause and you have an increased risk for another clot. If no mutations are found, then it is likely that the condition is due to another cause.
The risks that are associated with factor V Leiden, PT 20210, and other inherited and acquired factor deficiencies are independent. A person can have more than one risk factors for harmful blood clots, and their associated risks are cumulative. Added to inherited risks and acquired risks are controllable risk factors, such as use of oral contraceptives and hormone replacement therapy (HRT), that may worsen the combined underlying risk factors. For instance, if a woman has one gene copy with the factor V Leiden variant, she may be at about a 2 to 4 fold greater risk of developing a VTE. If she also uses oral contraceptives, the combined risk can increase to 35 times the risk for factor V Leiden heterozygosity alone, and women with factor V Leiden who take HRT have a 15-fold higher risk.
Sometimes, evaluation for the presence of a factor V Leiden mutation can begin with a test for activated protein C (APC) resistance, though it is not commonly performed nowadays. About 90% of the time, APC resistance is due to a factor V Leiden mutation, and the APC resistance ratio assay has a greater than 99% sensitivity for detecting a factor V Leiden mutation. If resistance is present, then a test for the factor V Leiden gene mutation is performed on the person's DNA, both to confirm the diagnosis and to determine whether the person has one or two copies of the mutation (is heterozygous or homozygous for the mutation).
Some studies have found a significant association between factor V Leiden mutation and recurrent miscarriages.
Several other tests may be used to help identify additional factors that may be contributing to excessive clotting (thrombophilia). Some of these include:
Regardless of the underlying cause, a VTE is usually treated with a short course of anticoagulants, often 3 to 12 months. A combination of heparin, warfarin, and low-molecular weight heparins or one of the newer oral anticoagulants may be prescribed. At the end of this time period, the person's risk level is reassessed to see if further treatment is necessary. Lifetime prophylactic treatment may be needed for some patients.
In general, no. Anticoagulant therapy is used when there is DVT and/or VTE. Long-term therapy may be considered for specific individuals, dependent upon the clinical situation. It should be noted that knowing whether a person with DVT/VTE has a factor V Leiden or prothrombin 20210 mutation does not change the intensity or duration of anticoagulant therapy.
No. If you have one of these mutations, they are part of your genetic make-up and they will not go away. However, there are things you can do to lower your risk of developing a blood clot, such as not smoking.
R2 (A4070G) is a mild factor V mutation believed to confer additional APC resistance when it is present in individuals who are heterozygous for FVL (R506Q). By itself, the R2 mutation is not known to significantly contribute to venous thrombosis risk.
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