Investigations

Investigations in DVT include the following:

• D-dimers
  • this is not a diagnostic test
  • generally a sensitive but nonspecific marker of DVT
    • estimated sensitivity and specificity is reported to be between75–100% and 26–83%, respectively
  • a raised level is suggestive (not conclusive) of a deep vein thrombosis but a negative test suggest a low possibility of DVT (especially if combined with the Wells scoring criteria ultrasound) (1,2)

Conformation of a clinically suspected DVT can be made by:

• venous ultrasound
  • is the first line DVT imaging modality
  • provides overall sensitivity of 94.2% for proximal, and 63.5% for isolated distal DVT, with an overall specificity of 93.8%
    • sensitivity is increased by combination with colour-Doppler ultrasound (but lowers sprcificity)
  • less accurate for asymptomatic above-knee DVT or isolated DVT of the calf
  • patients who have a negative or inadequate initial scan but who have a persisting clinical suspicion of DVT or whose symptoms do not settle should have a repeat US scan (1,2)
• contrast venography
  • a definitive investigation
  • presence of a constant intraluminal filling defect on at least two projections confirms the diagnosis
  • it is invasive and has limited value in patients with renal insufficiency and allergic reaction to contrast medium
• newer imaging techniques
  • computed tomography venography (CTV) and magnetic resonance venography (MRV)
  • sensitivity and specificity is similar to compression ultrasound
  • reserved for patients who cannot be evaluated properly by ultrasound or when thrombosis in pelvic veins or inferior vena cava is suspected (3)

Further investigations include:

• offer all patients diagnosed with unprovoked DVT who are not already known to have cancer the following investigations for cancer:
  • a physical examination (guided by the patient's full history) and
  • a chest X‑ray and
  • blood tests (full blood count, serum calcium and liver function tests) and
  • urinalysis
• consider
  • further investigations for cancer with an abdomino-pelvic CT scan (and a mammogram for women) in all patients aged over 40 years with a first unprovoked DVT or PE who do not have signs or symptoms of cancer based on initial investigation
  • testing for antiphospholipid antibodies in patients who have had unprovoked DVT or PE if it is planned to stop anticoagulation treatment
  • testing for hereditary thrombophilia in patients who have had unprovoked DVT or PE and who have a first‑degree relative who has had DVT or PE if it is planned to stop anticoagulation treatment (4).

Reference:

• (1) Scottish Intercollegiate Guidelines Network (SIGN) 2010. Prevention and Management of Venous Thromboembolism.
• (2) Stone J et al. Deep vein thrombosis: pathogenesis, diagnosis, and medical management. Cardiovasc Diagn Ther. 2017;7(Suppl 3):S276-S284
• (3) Wang K-L, Chu P-H, Lee C-H, et al. Management of Venous Thromboembolisms: Part I. The Consensus for Deep Vein Thrombosis . Acta Cardiologica Sinica. 2016;32(1):1-22
• (4) National Institute for Health and Care Excellence (NICE) 2015. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing