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    Deep Vein Thrombosis – Diagnosis

    Cardiovascular, Hematological / Oncological

    Last Updated Nov 23, 2020
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    By Nazde Edeer


    • Deep vein thrombosis (DVT) is common, with over 45,000 cases diagnosed in Canada each year.
    • Complications can include pulmonary embolism (PE) and post-thrombotic syndrome.
    • Risk factors for development of a DVT are closely related to Virchow’s triad (venous stasis, vascular injury and hypercoagulability) including recent surgery, immobilization, malignancy, trauma, pregnancy, estrogen use, and varicose veins.
    • Patients may present with calf pain or cramping, warmth, erythema and edema to a unilateral limb, primarily the lower limb.
    • 4-10% of DVT’s involve upper extremity:
      • 80% of these are secondary:
        • Pacemaker or Central Venous Catheters (including peripherally inserted central catheters (PICC line).
        • Anatomical: cervical rib; hypertrophy of scalenus muscle.
        • Trauma: clavicle fracture.
      • Paget-Schroetter syndrome:
        • Venous thrombosis of the subclavian vein in thoracic inlet syndrome.
        • Typically, young athletes.
        • Sports like baseball, swimming, or tennis.
      • Cancer
        • Pancoast tumor.
    • Diagnosis of DVT requires determining the pre-test probability of DVT either through clinical gestalt (depends on clinical experience) or better to use a clinical tool, such as the Well’s Score followed by D-dimer/ultrasound as indicated.

    Diagnostic Process

    • Thrombosis Canada recommends patients presenting with suspected DVT should be risk stratified. The most commonly used tool is the Well’s Score for DVT.

    • Wells Score > 2: DVT Likely
      • Perform Venous Compression Ultrasound (CUS) of the extremity
        • CUS is positive, initiate appropriate treatment for DVT.
        • CUS is negative, recommend performing a D-Dimer:
          • D-Dimer is negative, DVT can be ruled out.
          • D-Dimer is positive, repeat CUS in one week.
    •  Wells Score < 2: DVT Unlikely 
      • Perform a D-Dimer:
        • D-Dimer is negative, a DVT can be ruled out.
        • D-Dimer is positive, perform a CUS.
          • If the CUS is positive, a diagnosis of DVT can be made.
          • If the CUS is negative, DVT can be ruled out.
    • D-Dimer
      • D-Dimer is a marker of fibrin clot breakdown.
      • It is a highly sensitive (up to 90%) but non-specific test.
      • D-dimer can be elevated in many other conditions including:
        • Inflammatory diseases.
        • Infection.
        • Malignancy.
        • Advanced age – the use of an age-adjusted D-dimer cutoff has not been well validated for excluding DVT (unlike for PE). As such, its use for DVT diagnosis is not routinely recommended at this time by Thrombosis Canada.
        • Pregnancy.
        • Trauma.
        • Surgery.
      • In contrast to PE, there is no evidence to suggest that an age-adjusted D-dimer cutoff should be used to exclude DVT.
      • A D-dimer less than a fixed cut-off, in combination with validated clinical prediction rules (Wells score) can be used to rule out DVT in patients where DVT is deemed unlikely.


    Source: Diagnostic strategy adapted from Thrombosis Canada Deep Vein Thrombosis Diagnosis guideline.

    Quality Of Evidence?


    This diagnostic strategy has been approved and developed by Thrombosis Canada.


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