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DNA Analysis:
Factor V Leiden (R506Q) Mutation
Venous thrombosis is a serious health problem with an incidence of about 1 in 1,000 individuals per year. The incidence of thrombosis increases with age, from 1 in 100,000 during childhood to 1 in 100 per year in old age. There are both inherited and acquired predisposing factors for venous thrombosis, which may frequently interact. Inherited factors include resistance to activated protein C (APC) and deficiencies in antithrombin III, protein C, and protein S. APC resistance is the most common factor associated with inherited thrombophilia. Although there are other causes of APC resistance, up to 90% of individuals who are resistant to APC have the Factor V Leiden mutation. This mutation is the result of a substitution of adenine for guanine at nucleotide 1691 of the Factor V gene. The Factor V Leiden mutation has a prevalence of 2 - 5% in the general population. Heterozygous individuals have a 5 - 10 fold increase in risk for venous thrombosis. This risk may rise to as high as a 30 fold increase in smokers, obese individuals, and women on oral contraceptives. Homozygous individuals have a 50 – 100 fold increase in risk for venous thrombosis.
Molecular analysis for the Factor V Leiden (R506Q) mutation may be ordered individually or as part of a Thrombophilia Panel which includes the Prothrombin G20210A Mutation (Factor II) and the MTHFR (C677T) Variant.
- Individuals with a personal history of venous thrombosis before age 50
- Individuals with a family history of venous thrombosis
- Pregnant women or women taking oral contraceptives who have had a venous thrombotic event
- Women with recurrent pregnancy loss or unexplained preeclampsia, placental abruption, intrauterine fetal growth retardation, or stillbirth
- Women smokers with myocardial infarction before age 50
- Individuals with family members known to have the Factor V Leiden mutation
Direct mutation analysis: Our laboratory utilizes polymerase chain reaction and fluorogenic target-specific hybridization. Melting curve analysis is performed to discriminate between the normal and mutant genotype.
Approximately 90% of individuals with APC resistance have the Factor V Leiden mutation.
Blood: 5 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen may be refrigerated or stored at room temperature.
14 days
83891, 83898, 83912
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