Detecting the Factor V G1691A Mutation – Precision for Thrombophilia Risk Assessment

Factor V’s role in coagulation

Coagulation factor V is a key plasma glycoprotein in the blood-clotting cascade. In its activated form (Factor Va), it acts as a cofactor for Factor Xa, accelerating the conversion of prothrombin (Factor II) into thrombin. Thrombin then cleaves fibrinogen, resulting in fibrin formation — the fibrous mesh that gives structure to a clot.
Without proper regulation, this cascade may lead to excessive clot formation (thrombosis).

Factor V G1691A (Leiden) is a key marker in thrombosis risk assessment.

What is the G1691A (Leiden) mutation?

The G1691A substitution in the gene encoding Factor V results in a change of amino acid: an arginine is replaced by a glutamine at position 506 of the Factor V protein chain (commonly described as Arg506Gln or R506Q).
Because Arg506 is one of the key cleavage sites for the natural anticoagulant enzyme Activated protein C (APC), this mutation impairs the inactivation of Factor Va. The variant Factor Va remains active longer, sustaining thrombin generation and increasing the risk of pathologic clot formation.

Clinical significance

• The Factor V Leiden mutation is the most common inherited thrombophilia in people of European descent*.
• Heterozygous carriers (one mutated allele) have roughly a 5- to 10-fold increased risk of venous thromboembolism (VTE) compared with non-carriers.
• Homozygous carriers (two mutated alleles) face much higher risk — estimates suggest 30- to 80-fold increased risk of thrombosis.
• Additional risk factors (e.g., surgery, immobility, oral contraceptives, pregnancy) further magnify risk in mutation carriers.
• Because the mutation leads to activated-protein-C resistance, standard anticoagulation or thrombosis work-up often includes testing for this variant.

*The highest frequencies of the Leiden mutation are found in populations of European descent, particularly Northern/Western Europe. Frequencies drop substantially in non-European populations (e.g., much lower in Asians, Africans, some Latin American groups).

Why detection matters & how the kit helps

Early detection of the G1691A mutation enables clinicians and laboratories to:

• Identify individuals at elevated risk of VTE before an event occurs, helping guide prophylactic measures (especially in high-risk settings: surgery, pregnancy, contraception).
• Tailor anticoagulant strategies, monitoring, and lifestyle advice in carriers of the mutation.
• Support differential diagnosis of thrombophilia, especially in patients with unexplained or recurrent venous clots.
  According to clinical guidelines, molecular detection of this mutation (via PCR-based genotyping) is a valuable tool in the work-up of inherited thrombophilia.

Radovan Haluza