Faktor V Leiden

Background

The factor V Leiden polymorphism (1691G->A, R506Q) in the factor V gene (F5) is present in approximately 3% of the general population, and in about 20-50% of patients with a history of unexplained recurrent venous thrombosis. The presence of a glutamine (Q) instead of an arginine (R) residue removes a site in coagulation factor V that is normally cleaved by activated protein C, and is as-sociated with resistance to activated protein C. Presence of this polymorphism substantially increases the lifetime risk of venous thrombosis.

Factor V Leiden (F5 R506Q) genotypes

Genotype	Frequency	Commentary
F5 RR:	93%	Wild type genotype. No Factor V Leiden variant detectable.
F5 RQ:	7%	Heterozygous for factor V Leiden. The relative risk of venous thrombosis is increased approximately 3- to 8-fold.
F5 QQ:	< 0,1%	Homozygous for factor V Leiden. The relative risk of venous thrombosis is increased approximately 20- to 80-fold.

Indications for testing

According to the College of American Pathologists (CAP) Consensus Conference Statement, testing for factor V Leiden is recommended in patients with

a history of recurrent VTE, first VTE at younger than 50 years, or first unprovoked VTE at any age,

a first VTE at an unusual anatomic site, such as the cerebral, mesenteric, portal, or hepatic veins,

a first VTE, at any age, in a subject with a first degree family member with a VTE before the age of 50 years,

a first VTE related to pregnancy, the puerperium, oral contraceptive use, or hormone replacement therapy,

unexplained pregnancy loss during the second or third trimester.

Specimen Shipping

Literature:

Renner W et al. Prothrombin G20210A, factor V Leiden, and factor XIII Val34Leu: common mutations of blood coagulation factors and deep vein thrombosis in Austria. Thromb Res. 2000;99:35-9.
Segal JB et al. Predictive value of factor V Leiden and prothrombin G20210A in adults with venous thromboembolism and in family mem-bers of those with a mutation: a systematic review. JAMA. 2009;301:2472-85.