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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.
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.
Polymerase chain reaction (PCR) with restriction enzyme digestion and polyacrylamide gel electrophoresis
0.5 mL (Note: This volume does not allow for repeat testing.)
Maintain specimen at room temperature or refrigerate. Stable at room temperature and refrigerated for seven days.
Causes for Rejection
Clotted whole blood samples if adequate DNA not obtained; incorrect specimen type; frozen whole blood specimens