Genetic Testing for DVT in Patients Already on Apixaban
Genetic thrombophilia testing is not necessary for most patients with DVT who are already on apixaban (Eliquis), unless they meet specific criteria such as age under 50, unusual thrombosis sites, recurrent events, or strong family history. 1
When Thrombophilia Testing is Recommended
Thrombophilia testing should be performed in the following circumstances:
- Age <50 with venous thrombosis 2, 1
- Venous thrombosis in unusual sites (hepatic, mesenteric, cerebral veins) 2, 1
- Recurrent venous thrombosis 2, 1
- Venous thrombosis with strong family history of thrombotic disease 2, 1
- Venous thrombosis in pregnant women or women taking oral contraceptives 2, 1
- Women with recurrent pregnancy loss or unexplained severe pregnancy complications (preeclampsia, placental abruption, growth restriction, stillbirth) 1
When Testing May Be Considered
- Venous thrombosis in patients >50 years, except when active malignancy is present 2
- Relatives of individuals with venous thrombosis under age 50 2, 1
- Relatives of individuals known to have factor V Leiden or other thrombophilias 2
Testing Not Recommended
- Random screening of the general population 2
- Routine testing for patients with arterial thrombotic disorders (except young female smokers with MI) 2, 1
- Prenatal testing or routine newborn screening 2, 1
- Testing during acute thrombosis or initial 3-month period of anticoagulation 1
Impact on Management for Patients Already on Apixaban
For patients already on apixaban for DVT, thrombophilia testing has limited clinical utility in most cases 3. The decision to continue anticoagulation should be based primarily on:
- Clinical risk factors for recurrence
- Whether the DVT was provoked or unprovoked
- Patient's bleeding risk
Evidence suggests that optimal duration of anticoagulation should be based on clinical risks rather than thrombophilia test results 3. Apixaban is effective for treatment of DVT regardless of underlying thrombophilia status 4.
Important Considerations
The penetrance of thrombophilia genes varies significantly - lower in heterozygous carriers of Factor V Leiden and prothrombin 20210A (mild thrombophilia), and higher in carriers of deficiencies of antithrombin, protein C or S, and those with multiple or homozygous abnormalities (high-risk thrombophilia) 5
Patients with high-risk thrombophilia (antithrombin, protein C, or protein S deficiency) have significantly higher recurrence rates (19% at 2 years, 40% at 5 years) compared to those with Factor V Leiden or prothrombin mutation (7% at 2 years, 11% at 5 years) 6
Testing may be justified in specific cases where results would alter management decisions, such as determining indefinite anticoagulation for high-risk thrombophilias 1
Pitfalls to Avoid
- Testing during acute thrombosis or while on anticoagulation can affect results and lead to misinterpretation 1
- Normal test results do not exclude thrombophilia as there are likely factors yet to be discovered 3
- Assuming that a negative test means lower recurrence risk (clinical factors are more important) 3
- Testing without a clear plan for how results will change management 7
For a patient already on apixaban for DVT, focus on optimizing the duration of therapy based on clinical factors rather than pursuing thrombophilia testing unless the patient meets specific criteria that would alter management decisions.