Factor II – Factor V Leiden

Factor II and Factor V (Leiden) Genotyping

Factor V and II are blood clotting proteins. Variations to these proteins can increase the risk of dangerous cardiovascular events caused by venous thrombosis. Physicians should consider testing any patient who has had a personal or family history of such events or those at high clinical risk of venous thrombosis, including patients taking medications that are potential contributors.

Indication for Testing

Individuals with a personal or family history of first or recurrent venous thrombosis; who have had venous thrombosis at a young age (less than 50), venous thrombosis in unusual sites (hepatic, mesenteric, cerebral veins) or venous thrombosis in pregnancy; or those with a combination of these who are also taking medications which individually increase the risk for venous thrombosis.

Specimen Information
Please call Client Services at 800-837-8362 to order testing supplies.

Swabs: 4 sterile swabs
Blood: 5-10 cc whole blood lavender-top EDTA or Yellow-top ACD-A tubes
Turnaround Time: 7 business days, faster turnaround available for clinical trials

CPT Codes
Factor II and Factor V Mutation DNA Analysis (provided for your guidance only)
81241 and 81240

Additional Info

If you would like to learn more about Factor II and Factor V (Leiden), click here to view the short webinar, Factor V Leiden and Factor II 20210A Gene Mutations.

Clinical Significance

Variants to Factor V and Factor II can affect a patient’s risk of blood clotting problems. The Factor V variant known as Factor V Leiden (or rs6025) is associated with an approximately 300% increased risk in heterozygotes and an up to 8000% increased risk in homozygotes. The Factor II rs1799963 polymorphism (or G20210A) may also independently increase the risk approximately 200%.

Factor V testing is clinically actionable and recommended by the American College of Medical Genetics with Factor II as a tandem test. Patients should be counseled about the implications of their results by their physician or genetic counselor.

Certain polymorphisms show differing prevalence based on ethnic background.

Frequency of Factor II and Factor V alleles with clinical relevance

GeneAlleleEnzyme ActivityCaucasianAfricanHispanicNative AmericanAsian
Factor VLeiden (rs6025)Decreased2 – 5%1.23%2.21%0.45%1.25%
Factor IIrs1799963Decreased2.2%0.3-0.6%2.2%rarerare