3210. PCR. Thrombophilia. F5 gene (1691G>A)

The F5 gene encodes coagulation factor V, a key component of the blood-clotting cascade. The 1691G>A (F5 Leiden) mutation causes resistance to activated protein C, significantly increasing the risk of thrombosis, pregnancy complications, stroke, and other thromboembolic events.

F5 Leiden (1691G>A mutation) is the most common inherited cause of thrombophilia in the European population.

The mutation causes resistance of factor V to inactivation by activated protein C (APC resistance). As a result, normal anticoagulant regulation is impaired, promoting hypercoagulability and thrombosis.

Potential consequences of the F5 Leiden mutation:

• 6-9-fold increased risk of venous thrombosis in heterozygous carriers and up to 80-fold in homozygous carriers.
• Development of thrombosis at a young age, even in the absence of other risk factors.
• Pulmonary embolism (PE).
• Cerebral venous thrombosis and ischemic stroke.
• Increased risk of pregnancy complications, particularly:
  • second- and third-trimester pregnancy loss;
  • placental abruption;
  • preeclampsia;
  • fetoplacental insufficiency.

A significant increase in the risk of thrombosis when taking oral contraceptives or menopausal hormone therapy (MHT).

The test should be interpreted together with other genetic tests for thrombophilia (F2, MTHFR, PAI-1, F13A1, etc.), general clinical laboratory findings, and the patient’s clinical history.

• Women before starting combined oral contraceptives (COCs) or hormone replacement therapy (HRT).
• Women with a history of recurrent pregnancy loss, fetoplacental insufficiency, or preeclampsia.
• Individuals with a personal or family history of thrombosis, especially at a young age.
• Before planning a pregnancy or undergoing IVF.
• Patients with a history of thromboembolism, pulmonary embolism (PE), myocardial infarction, or stroke of unexplained cause.
• To clarify thrombophilia status as part of a comprehensive genetic evaluation.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: