The British Society for Haematology (BSH) has published new Clinical guidelines for testing for heritable thrombophilia.
The term thrombophilia is generally used to describe hereditary and/or acquired conditions associated with an increased predisposition to thrombosis. Heritable thrombophilia refers to genetic disorders of specific haemostatic proteins.
The most clearly defined heritable thrombophilias are
• the factor V Leiden (FVL) variant (F5 G1691A)
• the prothrombin gene variant (F2 G20210A)
• protein C (PC) deficiency
• protein S (PS) deficiency
• antithrombin (AT) deficiency
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Acquired thrombophilias:
• the antiphospholipid syndrome (APS)
• paroxysmal nocturnal haemoglobinuria (PNH)
• myeloproliferative neoplasms (MPN)
• the presence of a JAK2 mutation in the absence of an MPN phenotype.
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Routine testing of coagulation factors to assess the risk of thrombosis is not currently recommended.
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Deficiencies of physiological anticoagulants interact with acquired risks and a transient provoking factor is present in approximately 50% of episodes of venous thromboembolism (VTE) in genetically predisposed individuals. The risk of a first episode of VTE is increased around 15-fold in heterozygous AT deficiency. In those with heterozygous PC or PS deficiency, the risk of a first episode of VTE is increased around 5–7- fold.
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Genetic testing to identify causative variants of AT, PC, PS should be performed when the results will influence management. Genetic testing to predict a first episode of venous thrombosis is not recommended.
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Testing for heritable thrombophilic traits after a venous thrombotic event is not recommended as a routine to guide management decisions. Genetic testing for variants in genes (e.g., MTHFR, SERPINE1variants (PAI-1plasma level)) without a clinically significant link to thrombosis is not recommended.
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Testing for heritable thrombophilia is not recommended in patients with stroke, regardless of age.
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About testing of pregnant women we will talk in the next post.
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