Factor V Leiden (FVL) is a very common inherited thrombophilia associated with a moderate (3 to 5-fold) increased lifetime risk for venous thromboembolism (VTE), deep vein thrombosis being the most common. Treatment of VTE is not generally affected by FVL status and should follow standard guidelines. Genetic testing is not routinely recommended for the general population, those with unprovoked VTE (as it is unlikely to change management), VTE provoked by a surgical procedure, or for those with a family history of FVL. FVL carrier testing may be considered when the results of testing could affect clinical management:

• An unprovoked VTE involving unusual sites e.g. cerebral
• A VTE provoked by a nonsurgical major transient risk factor e.g. confinement to bed in hospital for at least three days
• A VTE provoked by pregnancy or occurring post-partum
• A VTE associated with the use of combined oral contraceptives
• A VTE at or under age 40 years, either spontaneous or associated with weak environmental risk factors, and at least one first-degree relativewith VTE

FVL carrier testing is indicated for those assigned female at birth (AFAB), planning a pregnancy and who have a family history of VTE and the potential for homozygous FVL in the individual (each parent of the individual is a carrier of FVL). Anticoagulation prophylaxis would be indicated for those with homozygous FVL. FVL carrier testing may also be considered for those AFAB and have a family history of VTE or have multiple VTE risk factors e.g. obesity, older age, comorbid medical conditions as postpartum prophylaxis may be considered.

For more details see the GECKO on the run for a concise summary.

The following tool contains:

• When would genetic testing be considered for factor V Leiden (FVL)
• Management recommendations for asymptomatic FVL carriers

Factor V Leiden point of care tool point of care tool (Jan 2023)

–

Disclaimer:

·           GECKO is an independent not-for-profit program that does not accept support from commercial or non-academic entities.

·           GECKO aims to aid the practicing non-genetics clinician by providing informed resources regarding genetic/genomic conditions, services and technologies that have been developed in a rigorous and evidence-based manner with periodic updating. The content on the GECKO site is for educational purposes only. No resource should be used as a substitute for clinical judgement. GECKO assumes no responsibility or liability resulting from the use of information contained herein.

·           All clinicians using this site are encouraged to consult local genetics clinics, medical geneticists, or specialists for clarification of questions that arise relating to specific patient problems.

·           All patients should seek the advice of their own physician or other qualified clinician regarding any medical questions or conditions.

·           External links are selected and reviewed at the time a page is published. However, GECKO is not responsible for the content of external websites. The inclusion of a link to an external website from GECKO should not be understood to be an endorsement of that website or the site’s owners (or their products/services).

·           We strive to provide accurate, timely, unbiased, and up-to-date information on this site, and make every attempt to ensure the integrity of the site. However, it is possible that the information contained here may contain inaccuracies or errors for which neither GECKO nor its funding agencies assume responsibility.