For investigators

Role of nurse / clinical trials practitioner

  • To liaise with research staff and undertake/support visits
  • To obtain informed consent for patients willing and able to participate in the trial
  • Venous samples and POC D-dimer test (blinded to patient and researcher)

Role of GP

  • To check for eligibility and acceptance of patients into trial
  • To report to the trial team any Adverse or Serious Adverse Events experienced by patients participating in the trial.

Role of Practice Receptionist

  • To provide a room for patient visits every 6 months

Trial recruitment

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 

Inclusion criteria

  • 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)

Exclusion criteria

  • 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.