Factor V Leiden Mutation Analysis

The Factor V (FV) Leiden mutation is present at a frequency of approximately 2-5% in the Caucasian population. The factor V protein is an important component of the coagulation cascade. The presence of the FV Leiden mutation prevents the degradation of FV causing a hypercoagulable state.

Clinical Features: The FV Leiden mutation is a significant risk factor for deep vein thrombosis (DVT). In the United States approximately half a million people per year are hospitalized due to venous thrombosis. DVT may present as a painful, swollen area (usually of the leg). If the thrombosis becomes dislodged it may manifest as a pulmonary embolism with shortness of breath, rapid heartbeat, arrhythmia or sudden death. Protein C or protein S deficiency or the presence of the FV Leiden mutation are all risk factors for DVT. The FV Leiden mutation is present in approximately 20-40% of individuals with symptoms of venous thrombosis, making it the most frequent risk factor associated with DVT.

Inheritance: Autosomal dominant with variable penetrance. Individuals with one copy of the mutation (heterozygous positive) have a 50% chance to pass the gene to each of their offspring.Those with two copies of the mutation (homozygous positive) have a 100% chance to pass the mutation to each of their offspring. Risks and risk factors: Heterozygotes with one copy of the FV Leiden mutation are at a 7-fold increased risk and homozygotes with two copies of the FV Leiden mutation are at an 80-fold increased risk for DVT. Homozygous positive individuals are expected to have at least one thrombotic event in their lifetime, while heterozygous individuals vary with respect to the expression of thrombotic problems. Risk factors that may trigger a thrombotic event include surgery, oral contraceptives, pregnancy, estrogen replacement therapy and trauma.

Indications and benefits: Testing is recommended for presymptomatic evaluation of at-risk individuals and for individuals with a history of DVT. Individuals who are found to be positive for the FV Leiden mutation can benefit from anticoagulant therapy and can advise other family members of their risks.

Test methodology: Polymerase chain reaction (PCR)* amplification and restriction enzyme digestion to detect the presence of the FV Leiden mutation (506Q) in the gene located at chromosome band 1q21-25. Results are reported as homozygous negative, heterozygous positive or homozygous positive.

Turnaround: Routine 2-3 weeks, Rush 7-10 days Additional resources: Factor V testing may have complex genetic issues. We recommend consultation with a Genetic Counselor in your area, or you may contact us at the following address

 

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