How many patients are involved?
Practices will be recruited through Primary Care Clinical Research and Trials Unit (PC-CRTU).
- 352 patients taking part in the study (and 316 completing the study). Allowing a 50% participation rate this means that 704 patients need to be approached initially.
- 704 patients invited from 10 hospital anticoagulant clinics and a minimum of 10 Primary care clinics
- 352 patients recruited
- 202 / 10 hospital sites = 20 per site = 10 per year
- 150 / 10 primary care clinics = 15 per site = 8 per year
- People aged 18 years or over with a diagnosis of first unprovoked proximal DVT or PE on treatment with anticoagulants
- Patients who have completed a minimum of 3 months of anticoagulant therapy (target 2-3)
- Patients under the age of 18 years
- Patients with another indication for long term warfarin therapy eg Atrial Fibrillation
- Patients with a diagnosis of first unprovoked proximal DVT or PE who are no longer on anticoagulation therapy
- Patients with a high risk of bleeding as evidenced by any of the following:
- Patients with a previous episode of major bleeding where the cause was not effectively treated
- Known thrombocytopenia with a platelet count of less than 120 x109 /L
- Known chronic renal failure with a creatinine of more than 150 µmols/L (1.7mg/dl) or eGFR less than 30
- Known chronic liver disease with a total bilirubin of more than 25µmols/L (1.5mg/dl)
- Active peptic ulcer
- Patients requiring antiplatelet therapy (eg Aspirin and/or Clopidogrel)
- Patients with a vena cava filter in place
- Patients who have had a D–dimer test performed within 2 months of potential enrolment other than for evaluation for suspected recurrent VTE that was not confirmed
- Patients whose GP expects their life expectancy to be less than 5 years
- Patients unable to attend follow up visits due to geographic inaccessibility
- Patients participating in a competing investigation
- Patients with known antiphospholipid syndrome
- If patients are subsequently found to have antiphosphlipid syndrome then they will have to be excluded.
- Patients with known inherited protein C and/or protein S or antithrombin deficiency
- If patients are subsequently found to have protein C and/or protein S or anithrombin deficiency then they will have to be excluded.
- Patients with a diagnosis of active cancer
- Patients unwilling to give consent
Definition of unprovoked VTE
The episode will be defined as unprovoked as long as there is no history within the previous 3 months of:
major surgery; lower limb trauma e.g. fracture, cast, limping for 3 days; use of the combined oral contraceptive pill or hormone replacement therapy ; pregnancy; significant immobility e.g. confined to bed for 3 days; active cancer.
Definition of Proximal
Proximal refers to a DVT in the trifurcation area, popliteal, superficial femoral, deep femoral, common femoral and iliac veins.