Factor V Leiden
Also known as: Factor V Leiden« Back to test list
The Factor 5 gene (F5) contributes to the normal coagulation cascade. A common variant in this gene, Factor V Leiden, is associated with an increased risk of thrombosis. The mutation causes resistance to activation of Factor 5 by activated protein C (APC); this is sometimes referred to as ‘APC resistance’.
The presence of one mutated F5 gene increases the risk of venous thrombosis by 3-8 fold and the risk of pregnancy loss by 2-3 fold. There is dispute regarding the clinical utility of this information in an unaffected patient, or in the management of an affected patient. The presence of two mutated F5 genes is associated with a higher risk of venous thrombosis.
This is an assay for heritable mutations. It may raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient. The interpretation of the result may also be dependent on the family history and the interpretation of other studies.
Analysis of the F5 gene for the specific Leiden mutation, c.1691G>A.
This test can be requested by any medical practitioner.
4 mL blood in EDTA (separate tube required). Specimens may be collected by the requesting practitioner or at any Sonic Healthcare pathology collection centre.
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We also recommend that the patient or another adult check the labelling of request forms and sample tubes.
Consider other genetic risk factors for thrombosis, for example, Prothrombin Genetic Test.