Genomics in general practice


Hereditary thrombophilia
☰ Table of contents


Practice point


Individuals who may benefit from genetic testing for hereditary thrombophilia include:

  • individuals with venous thromboembolism (VTE) <50 years of age without the following
    • major transient risk factor (eg surgery, immobility, trauma)
    • oestrogen provocation (eg pregnancy, prescribed oestrogens)
  •  individuals with VTE <50 years of age in an unusual site (eg central nervous system, abdominal veins, upper limb)1–3
  •  pregnant women who have had a previous episode of VTE or who have a strong family history of VTE (≥2 family members).1,4

Routine genetic testing for hereditary thrombophilia in individuals without any of the above features is not recommended in general practice.1

 

Box 1. Major hereditary thrombophilia conditions6

Group 1 conditions – Due to a defect or deficiency of an anticoagulant protein:

  • Antithrombin deficiency
  • Protein C deficiency
  • Protein S deficiency

Group 2 conditions – Due to genetic mutations that result in an increased tendency towards thrombosis:

  • Activated protein C resistance
  • Factor V Leiden
  • Prothrombin gene variant
  • Elevated levels of factors VIII, IX and XI

Other conditions:

  • Hyperhomocysteinaemia

The risk of thrombosis is higher for patients with Group 1 conditions than Group 2 conditions. Group 2 conditions occur approximately five times more frequently than Group 1 conditions.


What do I need to know?


Individuals with hereditary thrombophilia have an increased tendency to develop blood clots.

There are a number of different types of hereditary thrombophilia conditions (Box 1). At least half of thrombotic episodes in individuals with hereditary thrombophilia occur during periods of increased risk, such as during pregnancy, immobilisation or surgery.5

The risk of VTE in women taking a low-dose combined oral contraceptive (COC; <35 ug ethinyl oestradiol) is increased two to three times, compared with non-users. Despite this increase in risk, there is no indication for routine screening of women prior to prescribing a COC.5,7,8


Genetic testing


Testing practices for hereditary thrombophilia are variable across Australia, in part due a to lack of local evidence-based guidelines.2

Factor V Leiden and prothrombin variant genetic testing is only available on the Medicare Benefits Schedule (MBS) if the patient has a:9

  • personal history of VTE
  • family histroy of a diagnosed inherited thrombophilic condition.


When should I refer?


Refer women with hereditary thrombophilia who are pregnant or thinking about pregnancy. Management of hereditary thrombophilia in pregnancy requires specialised risk assessment, and patients should be under the direction of a specialist haematologist, obstetric physician or obstetrician.4,5


Other considerations


Patients diagnosed with hereditary thrombophilia should be encouraged to inform all first-degree relatives of increased risk; however, the benefit of cascade screening of relatives is uncertain.2,5,8,10


Resources for patients 


Centre for Genetics Education, Fact sheet 49: Blood clotting conditions (hereditary thrombophilias)
NHS Choices (UK), Thrombophilia
Varga E, The genetics of thrombophilia


Genomics in general practice




 

 

  1. Baglin T, Gray E, Greaves M, et al. Clinical guidelines for testing for heritable thrombophilia. Br J Haematol 2010;149(2):209–20.
  2. 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;195(3):139–42.
  3. Haematology Society of Australia and New Zealand and Choosing Wisely Australia. Tests, treatments and procedures clinicians and consumers should question. Sydney: NPS MedicineWise, 2016. [Accessed 20 December 2017].
  4. Gerhardt A, Scharf RE, Greer IA, Zotz RB. Hereditary risk factors for thrombophilia and probability of venous thromboembolism during pregnancy and the puerperium. Blood 2016;128(19):2343–49.
  5. Varga EA, Kujovich JL. Management of inherited thrombophilia: Guide for genetics professionals. Clin Genet 2012;81(1):7–17.
  6. Crowther MA, Kelton JG. Congenital thrombophilic states associated with venous thrombosis: A qualitative overview and proposed classification system. Ann Intern Med 2003;138:128–34.
  7. Bateson D, Butcher BE, Donovan C, et al. Risk of venous thromboembolism in women taking the combined oral contraceptive: A systematic review and meta-analysis. Aust Fam Physician 2016;45(1–2):59.
  8. Gialeraki A, Valsami S, Pittaras T, Panayiotakopoulos G, Politou M. Oral contraceptives and HRT risk of thrombosis. Clin Appl Thromb Hemost 2016:1076029616683802.
  9. Department of Health. Medicare benefits schedule book: Category 6. Canberra: DoH, 2017.  [Accessed 20 December 2017].
  10. National Institute for Health and Care Excellence. Venous thromboembolic diseases: Diagnosis, management and thrombophilia testing (CG144). London: NICE, 2012. [Accessed 20 December 2017].

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