From the Guidelines
For a patient with DVT on a heparin drip, I recommend ordering a hypercoagulability panel that includes tests unaffected by heparin therapy, such as genetic tests and antiphospholipid antibody testing, while deferring tests that are directly affected by heparin, like Protein C and S activity, antithrombin III levels, and fibrinogen levels, until at least 2 weeks after discontinuing anticoagulation. When considering hypercoagulable tests for a patient on heparin, it's crucial to understand which tests are reliable in this context. Genetic tests, including Factor V Leiden mutation, Prothrombin G20210A mutation, and MTHFR gene mutation, are not affected by heparin therapy and can be ordered as part of the initial workup 1. Antiphospholipid antibody testing, which includes anticardiolipin antibodies, lupus anticoagulant, and beta-2 glycoprotein I antibodies, can also be performed, although the interpretation of lupus anticoagulant may be challenging due to potential interference from heparin 1. However, tests such as Protein C and S activity, antithrombin III levels, and fibrinogen levels should be deferred until at least 2 weeks after discontinuing anticoagulation because heparin can directly affect these parameters, leading to falsely abnormal results 1. If evaluating for myeloproliferative disorders, testing for the JAK2 V617F mutation can be done while the patient is on heparin. It is essential to document the patient's anticoagulation status when interpreting results and consider repeating affected tests after completing anticoagulation therapy if the clinical situation allows. Given the potential for heparin to interfere with certain coagulation tests, focusing on genetic and antibody tests that remain reliable while on heparin is prudent, as suggested by recent guidance on laboratory detection and interpretation of antiphospholipid antibodies 1.
From the Research
Hypercoagulable Tests for DVT Patients on Heparin Drip
The following hypercoagulable tests can be ordered for a patient with Deep Vein Thrombosis (DVT) on a heparin drip:
- Factor V Leiden mutation test 2, 3, 4
- Prothrombin gene mutation test 3
- Protein C deficiency test 5, 6
- Protein S deficiency test 5, 6
- Antithrombin deficiency test 5, 6
- Lupus anticoagulant test 4
- Anti-cardiolipin antibody test 5
- Homocysteine level test 6
- Factor VIII level test 6
- ADAMTS13 activity test 6
- Heparin cofactor II activity test 6
- Plasminogen level test 6
- Tissue factor pathway inhibitor (TFPI) level test 6
- Thrombomodulin level test 6
- Protein Z level test 6
- Plasminogen activator inhibitor-1 (PAI-1) level test 6
- Thrombin-activatable fibrinolysis inhibitor (TAFI) level test 6
- Endothelial protein C receptor (EPCR) level test 6
- Factor XIII Val34Leu mutation test 6
Rationale for Test Selection
These tests are selected based on their association with an increased risk of venous thromboembolism, as well as their potential to guide anticoagulant therapy 5, 2, 3, 4, 6. The results of these tests can help identify underlying hypercoagulable conditions that may contribute to the development of DVT, and inform the selection of appropriate anticoagulant therapy.
Considerations for Test Interpretation
It is essential to consider the clinical context and patient-specific factors when interpreting the results of these tests 3, 4, 6. The presence of one or more hypercoagulable conditions may increase the risk of recurrent venous thromboembolism, and guide the selection of extended anticoagulation therapy 5, 3, 4.