Pro-thrombin and Factor V Leiden

The annual incidence of venous thromboembolism (deep vein thrombosis and pulmonary embolism) is approximately 117 per 100,000 persons or about 1 per 1,000 person-years. ACMG selected two mutations associated with increased risk for occurrence/recurrence of venous thrombosis—the factor V Leiden and the prothrombin 20210G>A (factor II) 1

Prothrombin and Factor V Leiden are genetic mutations associated with an increased risk of blood clot formation. Prothrombin refers to a protein involved in the blood clotting process, while Factor V Leiden refers to a specific mutation in the Factor V gene, which affects the activity of a clotting protein called Factor V.

Individuals with these mutations have an altered blood clotting mechanism, making them more susceptible to developing abnormal blood clots, a condition known as thrombophilia. This increased clotting tendency can lead to various health issues, including deep vein thrombosis (DVT), pulmonary embolism (PE), and other clot-related complications. Prothrombin and Factor V Leiden mutations can be associated with an increased risk of miscarriages and may be considered as part of the evaluation for recurrent pregnancy loss.

When should you get tested?

  • Individuals who have a personal or family history of blood clots, particularly deep vein thrombosis (DVT) or pulmonary embolism (PE).
  • Individuals or couples who have experienced multiple unexplained pregnancy losses.
  • Testing may be advised before initiating hormonal contraception (such as birth control pills) or hormone replacement therapy (HRT) in women.
  • Testing may be considered before major surgeries or periods of prolonged immobilization.
  • If there is a known family history of Prothrombin or Factor V Leiden mutations

Test specifications

TechniqueVariant typesTATSample requirements
Sanger sequencing Mutation3 - 4 weeks2 ml EDTA Blood / 2 ug DNA


  1. Spector, Elaine B., et al. "Technical standards and guidelines: venous thromboembolism (Factor V Leiden and prothrombin 20210G> A testing): a disease-specific supplement to the standards and guidelines for clinical genetics laboratories." Genetics in Medicine 7.6 (2005): 444-453.
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