Clinical Opal - thrombophilia testing after a DVT
It is 3PM on a Thursday afternoon and your next patient is Dimitri, a 54 year old groundsman. Dimitri is attending for review after a recent lower leg DVT following a knee arthroscopy. He was commenced on apixaban at the time of diagnosis and is doing well.
Dimitri asks you whether he should be tested for a “clotting disorder”. His neighbour suggested that he talk to you and have a blood test to “make sure it doesn’t happen again”. He has never had a previous clot and has no family history. He is a non-smoker.
What do you advise Dimitri about thrombophilia testing?
Clinical guidelines recommend against thrombophilia testing in Dimitri’s case.
In 2019, the Thrombosis and Haemostasis Society of Australia and New Zealand (THANZ) published new guidelines in the MJA on the diagnosis and management of venous thromboembolism (VTE), including recommendations for thrombophilia testing.1 They stated that patients with VTE provoked by surgery or major trauma should not be screened for hereditary thrombophilia.
There are a number of factors underpinning this recommendation. The presence of an inherited thrombophilia does not influence initial anticoagulant treatment. The predictive value of recurrent VTE conferred by the most common types of heritable thrombophilia (factor V Leiden and the prothrombin mutation) is limited. And the risk of recurrence associated with rare deficiencies of natural anticoagulants (antithrombin, protein C and protein S) is unclear.2
The guidelines state that it is reasonable to test in some specific scenarios:
- Young patients (< 45 years) with unprovoked proximal VTE should be tested for antithrombin and protein C and S deficiency if it influences treatment duration
- Patients with unprovoked proximal DVT and PE should be tested for antiphospholipid syndrome.
Additional important practice points include:
- Patients should be counselled regarding the potential significance of thrombophilia screening prior to testing
- Testing may be inaccurate in the presence of anticoagulation
- Patients with unprovoked proximal DVT and PE should be evaluated for malignancy by a thorough clinical assessment and age- and risk factor-appropriate screening.
For more information:
The rational use of pathology tests is a challenging area of general practice. Medcast have developed a free multimedia educational program, 'Testing, testing 1, 2, 3', to support GPs to use pathology tests more effectively, and reduce the harms of non-rational test ordering.
References
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Ho WK, Hankey GJ, Eikelboom JW. Should adult patients be routinely tested for heritable thrombophilia after an episode of venous thromboembolism? Med J Aust. 2011 Aug 1;195(3):139-42.
Simon is a GP based in Newcastle, NSW, and a senior medical educator with Medcast. He also has medical education roles with the RACGP and GPSA.
Over the past three decades, Simon has worked in clinical and educational roles in NSW and the NT, as well as in the Republic of Ireland. He has published over 75 peer reviewed journal articles, and in 2018 received the RACGP Corliss award for his contribution to medical education.
Simon is passionate about high quality education and training. He has particular interests in GP supervisor professional development and the rational use of tests and medicines. He is a proud member of Doctors for the Environment. He spends his spare time drinking craft beer and pretending that he is a musician in the Euthymics, an all-GP band.
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