Deep Vein Thrombosis (DVT)

Two-level Wells Score

Clinical probability simplified score

• DVT likely: 2 points or more
• DVT unlikely: 1 point or less

If a DVT is 'likely' (2 points or more)

• a proximal leg vein ultrasound scan should be carried out within 4 hours
  • if the result is positive then a diagnosis of DVT is made and anticoagulant treatment should start
  • if the result is negative a D-dimer test should be arranged. A negative scan and negative D-dimer makes the diagnosis unlikely and alternative diagnoses should be considered
• if a proximal leg vein ultrasound scan cannot be carried out within 4 hours a D-dimer test should be performed and interim therapeutic anticoagulation administered whilst waiting for the proximal leg vein ultrasound scan (which should be performed within 24 hours)
  • interim therapeutic anticoagulation used to mean giving low-molecular weight heparin
  • NICE updated their guidance in 2020. They now recommend using an anticoagulant that can be continued if the result is positive.
  • this means normally a direct oral anticoagulant (DOAC) such as apixaban or rivaroxaban
• if the scan is negative but the D-dimer is positive:
  • stop interim therapeutic anticoagulation
  • offer a repeat proximal leg vein ultrasound scan 6 to 8 days later

If a DVT is 'unlikely' (1 point or less)

• perform a D-dimer test
  • this should be done within 4 hours. If not, interim therapeutic anticoagulation should be given until the result is available
  • if the result is negative then DVT is unlikely and alternative diagnoses should be considered
  • if the result is positive then a proximal leg vein ultrasound scan should be carried out within 4 hours
  • if a proximal leg vein ultrasound scan cannot be carried out within 4 hours interim therapeutic anticoagulation should be administered whilst waiting for the proximal leg vein ultrasound scan (which should be performed within 24 hours)

D-dimer tests

• NICE recommend either a point-of-care (finger prick) or laboratory-based test
• age-adjusted cut-offs should be used for patients > 50 years old

Management

Choice of anticoagulant

• the big change in the 2020 guidelines was the increased use of DOACs
• apixaban or rivaroxaban (both DOACs) should be offered first-line following the diagnosis of a DVT
  • instead of using low-molecular weight heparin (LMWH) until the diagnosis is confirmed, NICE now advocate using a DOAC once a diagnosis is suspected, with this continued if the diagnosis is confirmed
  • if neither apixaban or rivaroxaban are suitable then either LMWH followed by dabigatran or edoxaban OR LMWH followed by a vitamin K antagonist (VKA, i.e. warfarin)