Medical Genetics

Prothrombin G20210A Mutation (Factor II)

Genetic predisposing factors for venous thrombosis include elevated plasma prothrombin levels. Increased plasma prothrombin levels are associated with the presence of the G20210A point mutation in the prothrombin (factor II) gene. This mutation is the result of a substitution of adenine for guanine at nucleotide 20210 in the prothrombin gene. The prothrombin (G20210A) mutation has a prevalence of approximately 2% in Caucasian populations. The mutation is rare in other ethnic groups. Heterozygous individuals have a 2-3 fold increase in risk for venous thrombosis.

Molecular analysis for the prothrombin (G20210A) mutation may be ordered individually or as part of a Thrombophilia Panel which includes the Factor V Leiden (R506Q) Mutation and the MTHFR (C677T) Variant.

Indications for Testing

Individuals with a personal history of venous thrombosis

Individuals with a family history of venous thrombosis

Pregnant women or women taking oral contraceptives who have had a venous thrombotic event

Individuals with family members known to have the prothrombin G20210A mutation

Testing Methodology

Direct mutation analysis: Our laboratory utilizes polymerase chain reaction and fluorogenic target-specific hybridization. Melting curve analysis is performed to discriminate between the normal and mutant genotype.

Sensitivity

Approximately 6 - 8% of individuals with a first episode of venous thrombosis have the prothrombin (G20210A) mutation. Approximately 20% of families with history of venous thrombosis have the prothrombin (G20210A) mutation.

Specimen Requirements

Blood: 5 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen may be refrigerated or stored at room temperature.