From the Guidelines
Testing for Methylenetetrahydrofolate Reductase (MTHFR) and Factor V Leiden blood clotting disorders requires specific genetic tests, which should be performed using accepted technical approaches, as long as they have been properly validated by the laboratory, while adhering to current quality assurance guidelines for molecular genetic testing 1.
Key Points to Consider
- For both conditions, a healthcare provider will order a blood test that analyzes your DNA for the specific genetic mutations.
- The MTHFR test looks for mutations in the MTHFR gene (commonly C677T and A1298C variants), while the Factor V Leiden test examines the F5 gene for the R506Q mutation.
- These tests typically require a standard blood draw, with results usually available within 1-2 weeks.
- No special preparation is needed before testing.
- Your doctor may recommend these tests if you have a personal or family history of blood clots, recurrent pregnancy loss, or cardiovascular disease at a young age, as outlined in the american college of medical genetics consensus statement on factor v leiden mutation testing 1.
Recommendations for Testing
- Testing should be performed in at least the following circumstances:
- Age <50, any venous thrombosis.
- Venous thrombosis in unusual sites (such as hepatic, mesenteric, and cerebral veins).
- Recurrent venous thrombosis.
- Venous thrombosis and a strong family history of thrombotic disease.
- Venous thrombosis in pregnant women or women taking oral contraceptives.
- Relatives of individuals with venous thrombosis under age 50.
- Myocardial infarction in female smokers under age 50, as recommended by the american college of medical genetics consensus statement on factor v leiden mutation testing 1.
Important Considerations
- Random screening of the general population for factor V Leiden is not recommended, as stated in the american college of medical genetics consensus statement on factor v leiden mutation testing 1.
- Routine testing is not recommended for patients with a personal or family history of arterial thrombotic disorders (e.g., acute coronary syndromes or stroke) except for the special situation of myocardial infarction in young female smokers.
- If positive, your doctor might recommend preventive measures like avoiding hormonal contraceptives for Factor V Leiden carriers or possibly supplementing with folate for certain MTHFR mutations.
From the Research
Testing for MTHFR and Factor V Leiden Blood Clotting Disorders
To test for Methylenetetrahydrofolate Reductase (MTHFR) and factor V Leiden blood clotting disorders, the following methods can be employed:
- Genetic testing to identify mutations in the MTHFR and factor V Leiden genes, as seen in studies 2, 3
- Blood tests to measure the levels of homocysteine, which can be elevated in individuals with MTHFR mutations 2
- Tests to evaluate blood clotting factors, such as prothrombin time and activated partial thromboplastin time, which can be affected by factor V Leiden mutations 4, 5
Diagnostic Criteria
The diagnostic criteria for MTHFR and factor V Leiden blood clotting disorders include:
- Presence of one or more mutations in the MTHFR or factor V Leiden genes, as identified by genetic testing 2, 3
- Elevated levels of homocysteine in the blood, which can indicate MTHFR mutations 2
- Abnormal blood clotting factor levels, such as prothrombin time and activated partial thromboplastin time, which can indicate factor V Leiden mutations 4, 5
Risk Factors and Associations
MTHFR and factor V Leiden blood clotting disorders have been associated with various risk factors and conditions, including:
- Increased risk of venous thromboembolism (VTE) and arterial disease, as seen in studies 4, 5, 3
- Myocardial infarction, particularly in individuals with combined MTHFR and factor V Leiden mutations 2
- Recurrent pregnancy loss, as seen in study 4
- Hypercoagulable states, which can increase the risk of blood clots and thrombosis 6