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

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.

Routine testing of coagulation factors to assess the risk of thrombosis is not currently recommended.

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.

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.

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.

Testing for heritable thrombophilia is not recommended in patients with stroke, regardless of age.

About testing of pregnant women we will talk in the next post.