Test Directory

This test provides information about additional risk for venous thrombosis among individuals known to be heterozygous for factor V Leiden (one copy of mutation). This knowledge aids in prevention of venous thrombosis. Factor V Leiden is the most common genetic risk factor for venous thrombosis and pulmonary embolism. It is present in 5% of the Caucasian population and in 20% to 40% of individuals with a history of venous thromboembolism. Not all individuals who are heterozygous for factor V Leiden will experience a thrombotic event, and the factor V R2 DNA analysis identifies some individuals at risk. Factor V Leiden heterozygotes are at a sevenfold increased risk for venous thrombosis compared to the general population. Coexistence of the R2 polymorphism with factor V Leiden increases that risk by an additional threefold, leading to an increased risk of approximately 16-fold.

Specimen Type: Whole Blood

Preferred Collection Container: Lavender Top (EDTA)

Alternate Collection Container: Pale Yellow Top (ACD)

Desired Specimen Volume: 5 mL

1. Collect a lavender top (EDTA) tube via venipuncture.

1. Transport whole blood in the original collection container.

Transport to the laboratory at room temperature.  

• Clotted whole blood samples if adequate DNA not obtained
• Incorrect specimen type
• Frozen whole blood samples

 See patient report.

This is not a diagnostic test. It assesses increased risk of venous thromboembolism due to the presence of the factor V R2 variant in individuals who are heterozygous for factor V Leiden. Not all individuals with factor V R2 and factor V Leiden will have a venous thrombosis event in their lifetimes. Test results should be used in conjunction with clinical observation and other lab results.

•  Factor V R2 DNA Analysis