• Thrombophilias are conditions which predispose an individual to thrombosis. They are relatively uncommon conditions. They include:
  • Enhanced activity of pro-coagulants.
    • Factor V Lieden mutation.
    • Prothrombin gene mutation.
  • Deficiency in natural anticoagulants.
    • Protein C
    • Protein S
    • Antithrombin III
  • Antiphospholipid Syndrome
    • Leads to both venous and arterial thrombus and associated with recurrent miscarriages.
    • Investigate for antiphospholipid syndrome by screening for the following antibodies:anticardiolipin antibody, lupus anticoagulant, Beta2 glycoprotein antibody.

• Thrombophilias should not be investigated routinely as the conditions are relatively uncommon and management does not change substantially.
• You may consider investigating if:
  • Site of the thrombus is unusual such as in the cerebral venous system.
  • Strong family history of thrombosis.
  • Recurrent miscarriage.

Investigating for thrombophilia

• Timing of testing is important as both the DVT itself (which can deplete certain coagulants) and the treatment of the DVT (warfarin in particular) will make testing inaccurate.
• Testing for factor V Leiden mutation and prothrombin mutation are not affected by anticoagulation therapy or presence of a DVT.
• Further screening is usually performed after the anticoagulation therapy is ceased.

• The presence of provoking factors determines the length of anticoagulation.
  • Provoked DVT – 3-6 months.
  • Unprovoked – consideration of life-long anticoagulation.

• Acute
  • Look for evidence of vascular compromise: if present then contact the vascular team and consider catheter guided thrombolysis.
  • Anticoagulation
    • Warfarin
    • Direct thrombin inhibitor – Dabigatran
    • Factor Xa inhibitors – Rivaroxaban, Apixaban
    • These latter 3 agents do not require bridging with heparin therefore are beneficial for those presenting to the Emergency Department or GP.

NB: Direct thrombin inhibitors and Factor Xa inhibitors are contraindicated in renal failure.

• Long term
  • Compression stockings are helpful with patients with post thrombotic syndrome (presence of pain and swelling in the leg after resolution of the DVT).
  • Ensure adequate follow up so that the cessation of therapy can be considered in an appropriate time frame.

• Above knee DVTs
  • Should always be treated with anticoagulation.
• Below knee DVTs
  • Controversial. Can be treated with anticoagulation, or a repeat Doppler performed in 2 weeks, and if there is extension then treatment is commenced.

• Diagnosis of DVT is important as it can cause significant morbidity and mortality.
• When making the diagnosis always ask for provoking factors as this will determine the length of anticoagulation.
• Thrombophilia testing is complex and should only be performed is selected cases.