Prothrombin mutation, also called Factor II genotype or F2 genotype, is a genetic blood test that analyzes whether you carry the F2 G20210A variant in prothrombin. The variant can lead to elevated levels of prothrombin and is associated with an increased risk of venous thrombosis.
What does a prothrombin mutation test show?
The test analyzes a specific genetic variant in the F2 gene, which codes for the coagulation protein prothrombin, also called Factor II. Prothrombin is an important part of the blood coagulation system and helps the blood to heal after an injury.
The F2 G20210A variant can cause the body to produce more prothrombin than normal. This can increase the tendency to form blood clots, especially in the veins. Examples of venous blood clots include deep vein thrombosis in the leg and pulmonary embolism.
Interpretation of test results for prothrombin mutation
- Genotype G/G is normal. The analyzed variant has not been detected.
- Genotype G/A means that variants have been detected in one of the gene copies and are associated with an increased risk of venous thrombosis.
- Genotype A/A means that variants have been detected in both gene copies and are associated with an increased risk of venous thrombosis. .
- have had a venous blood clot at a young age
- have had recurrent blood clots
- have close relatives with venous thrombosis or a known prothrombin mutation
- have had a blood clot without a clear triggering cause
- have had a blood clot in an unusual location
- are being investigated prior to treatment or situations that may increase the risk of thrombosis
A detected mutation does not mean that you will definitely suffer from a blood clot. The individual risk is also influenced by other factors, such as previous thrombosis, heredity, pregnancy, estrogen therapy, smoking, obesity, surgery, prolonged immobilization and other coagulation disorders.
When may it be relevant to test for prothrombin mutation?
A genetic test for prothrombin mutation may be relevant in the investigation of suspected hereditary thrombotic predisposition, especially if you:
Is prothrombin mutation hereditary?
Yes. The variant is hereditary and can be passed on from parent to child. If a person has the variant in one of their two gene copies, it can be passed on to the next generation. A genetic finding can therefore sometimes be relevant even for close biological relatives.
Is the test affected by blood-thinning drugs?
No. Since the analysis examines DNA, the result is not affected by anticoagulation treatment. The test can be performed even if you are using blood-thinning drugs.
Analysis method
Analysis performed with probe-based real-time PCR regarding nucleotide 20210 in the prothrombin gene, also called the Factor II gene. The analysis is performed on DNA extracted from blood.
Important things to know about the test
The test only analyzes the F2 G20210A variant and does not provide a complete assessment of your overall risk of blood clots. In a broader thrombosis investigation, other analyses may also be relevant, such as Factor V Leiden, antithrombin, protein C and protein S. The result should always be interpreted together with medical history, heredity and other risk factors.



