Factor V (Leiden) Mutation Analysis

This test detects the presence or absence of only 1 pathogenic variant (mutation) in the factor V (F5) gene. This variant is known as factor V Leiden, R506Q, orc.1601G>A. An individual who is heterozygous has 1 copy of the factor V gene that carries the Leiden variant and 1 copy that does not carry the variant. Individuals who are heterozygous carriers of the Leiden variant have an increased risk for thromboembolism. This increased risk is not as high as that conferred by 2 copies (homozygous) of the factor V Leiden variant.

The coagulation pathway is complex, and it is important to interpret the factor V Leiden results in the context of other genetic results, environmental exposures (such as smoking), personal history of thrombosis, and family history of thrombosis.¹

While the Leiden variant (mutation) is the most common variant tested for in the factor V gene, the gene is large, and many different variants affecting its function have been described. It is important to confirm that the patient’s relative had genetic testing for factor V Leiden and that factor V Leiden is the cause of the relative’s thrombophilia before interpreting the patient’s result.

If the relative is confirmed heterozygous or homozygous for factor V Leiden and the patient is negative for this variant, the patient’s risk of thrombosis is reduced to that of the general population, provided that all other thrombosis risk factors have been taken into consideration. 

No, this testing is not affected by medications.