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Factor V Leiden Mutation Analysis

CPT:

81241


Synonyms

Factor VLeiden DNA Test;



Specimen Requirements


Specimen

Whole blood or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab)


Volume

7 mL whole blood or LabCorp buccal swab kit


Minimum Volume

3 mL whole blood or two buccal swabs


Container

Lavender-top (EDTA) tube, yellow-top (ACD) tube, or LabCorp buccal swab kit


Storage Instructions

Maintain specimen at room temperature.


Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab


Test Details


Use

Detection of Leiden (R506Q) mutation in factor V gene (OMIM 227400), causing increased risk of thrombosis


Limitations

This test detects the factor V R506Q (Leiden) mutation and will help identify those individuals who are at increased risk of thrombosis; however, increased risk of thrombosis can be caused by a variety of genetic and nongenetic factors not screened for by this assay.


Methodology

Allele-specific polymerase chain reaction (PCR) and gel electrophoresis


Pregnancy Week

0–13 Weeks
14–21 Weeks
22+ Weeks

Additional Information

Details of how the blood coagulation system is regulated have become well understood in recent years. Many of the abnormalities that cause some patients to have an increased risk for thrombosis have been defined at the molecular level. The poor anticoagulant response to activated protein C (APC), or APC resistance, that is found in up to 50% of patients with a family history of thrombosis, and in 3% to 8% of apparently normal individuals, was shown to correlate with the inheritance of a single-point mutation in the factor V gene. This mutation has been reported in patients with deep vein thrombosis, pulmonary embolus, central retinal vein occlusion, cerebral sinus thrombosis, and hepatic vein thrombosis. Ten percent to 20% of people with a first-time venous clot have this mutation. Strikingly, 40% of people younger than 50 with a first-time venous clot, and 60% of pregnant women with venous thrombosis have this mutation as well. Beyond the risk for thrombophilia, this mutation has also been associated with an increased risk for recurrent pregnancy loss, severe pre-eclampsia, fetal growth retardation, stillbirth, and placental problems (infarction and abruption).

The mutation is characterized by a guanine to adenine substitution at nucleotide 1691 in exon 10 of the factor V gene that replaces an arginine at codon 506 with a glutamine. It is designated as FV R506Q (Leiden), and confers resistance to inactivation by activated protein C. As a result, factor V persists in the circulation, leading to a mild hypercoagulable state. The Leiden mutation accounts for 90% to 95% of APC resistance. Heterozygous carriers of this mutation have a four- to eightfold increased risk of thrombosis. Individuals homozygous for the mutation (ie, they have a copy of the mutation on each chromosome) carry an 80- to 100-fold risk of thrombosis. All offspring of a factor V Leiden homozygote will inherit at least a single copy of the mutation. Genetic counseling is recommended for these patients.

The risk of venous thrombosis increases exponentially in patients with more than one risk factor, including age, surgery, oral contraceptive use, pregnancy, elevated homocysteine levels, or malignancy. A 2005 study reports malignancy carries a sevenfold increased risk for thrombosis, and that this effect is most pronounced for hematological malignancies, for recently diagnosed cancers, and/or for patients with distant metastases. Malignancy and genetic predisposition together may compound risk, as carriers of the factor V Leiden mutation who have cancer are more likely to develop thrombosis than mutation carriers without cancer. Other risk factors to be considered in the work-up for venous thrombosis include the G20210A mutation in the factor II (prothrombin) gene, mutations in the MTHFRgene, protein S and C deficiency, and antithrombin deficiencies. Anticardiolipin antibody and lupus anticoagulant analysis may be appropriate for certain patients, as well as homocysteine levels. Genetic counselors are available for health care providers to discuss results, and for information on how to order additional testing, if desired, at 800-345-4363.


References

Blom JW, Doggen CJ, Osanto S, Rosendaal FR. Malignancies, prothrombotic mutations, and the risk of venous thrombosis. JAMA. 2005 Feb 9; 293(6):715-722. PubMed 15701913

College of American Pathologists Consensus Conference XXXVI: Diagnostic Issues in Thrombophilia. Arch Pathol Lab Med. 2002; 126(11):1277-1433. PubMed 12421135

De Stefano V, Martinelli I, Mannucci PM, et al. The risk of recurrent deep venous thrombosis among heterozygous carriers of both factor V Leiden and the G20210A prothrombin mutation.N Engl J Med. 1999 Sep 9; 341(11):801-806. PubMed 10477778

Grody WW, Griffin JH, Taylor AK, et al. American College of Medical Genetics consensus statement on factor V Leiden mutation testing. Genet Med. 2001 Mar-Apr; 3(2):139-148.PubMed 11280951

Laffan M, Tuddenham E. Thrombophilia: An expanding group of genetic defects that predispose to thrombosis. Mol Med Today. 1997 Jul; 3(7):303-309. PubMed 9257298

Reich LM, Bower M, Key NS. Role of the geneticist in testing and counseling for inherited thrombophilia.Genet Med. 2003 May-Jun; 5(3):133-143. PubMed 12792420

Van Cott EM, Soderberg BL, Laposata M. Activated protein C resistance, the factor V Leiden mutation, and a laboratory testing algorithm. Arch Pathol Lab Med. 2002 May; 126(5):577-582. PubMed 11958664

Voelkerding KV. Resistance to activated protein C and a novel factor V gene mutation. Clin Lab Med. 1996 Mar; 16(1):169-186 (review). PubMed 8867589


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