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    Wells' Criteria for DVT

    Calculates Wells' Score for risk of DVT.


    Note: The Wells' Score is less useful in hospitalized patients. (Silveira PC, 2015)

    When to Use
    Why Use

    The Wells’ DVT Criteria can be used in the outpatient and emergency department setting. By risk stratifying to low risk (Wells’ Score <2) and a negative d-dimer the clinician can exclude the need for ultrasound (US) to rule out DVT.

    The Wells’ Deep Vein Thrombosis (DVT) Criteria risk stratify patients for DVT.

    • There is an overall low prevalence of DVT in cases with low (<25%) clinical suspicion patients.
    • The Wells score inherently incorporates clinical gestalt with a minus 2 score for alternative diagnosis more likely.
    • Sequelae from DVT include pulmonary embolism (PE) and pulmonary hypertension, which have an associated mortality of 1-8%.
    • Anticoagulation is the mainstay treatment for DVT with its own associated risks of bleeding.

    Traditional testing for DVT involved multiple lower extremity US which are associated with time and cost. Utilization of the Wells’ DVT criteria can determine those patients who are overall unlikely to have a DVT. Further testing with d-dimer can safely rule out DVT without the need for US.


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    Creator Insights


    • As with all clinical decision aids, the Wells’ DVT criteria is meant to aid clinical decision making and not force management.
    • The Wells’ DVT criteria should only be applied after a detailed history and physical is performed.
    • The Wells’ DVT criteria should only be applied to those patients who have been deemed at risk for DVT. If there is no concern for DVT than there is no need for risk stratification.


    Patients can be divided into “DVT unlikely” and “DVT likely” groups based on Wells score. An additional moderate risk group can be added based on the sensitivity of the d-dimer being used.

    • A score of 0 or lower is associated with DVT unlikely with a prevalence of DVT of 5%.
      • These patients should proceed to d-dimer testing:
        • A negative high or moderate sensitivity d-dimer results in a probability <1 % and no further imaging is required.
        • A positive d-dimer should precede to US testing
          • A negative US is sufficient for DVT rule out.
          • A positive US is concerning for DVT; strongly consider treatment with anticoagulation.
    • A score of 1-2 is considered moderate risk with a pretest probability of 17%.*
      • These patients should proceed to high-sensitivity d-dimer testing (moderate sensitivity d-dimer is not sufficient).
        • A negative high-sensitivity d-dimer is sufficient for rule out of DVT in a moderate risk patient with a probability of <1%.
        • A positive high sensitivity d-dimer should precede to US testing.
          • A negative US is sufficient for ruling out DVT.
          • A positive US is concerning for DVT, strongly consider treatment with anticoagulation 
    • A score of 3 or higher suggests DVT is likely. Pretest probability 17-53%.
      • All DVT likely patients should receive a diagnostic US.
      • D-dimer testing should be utilized to help risk-stratify these DVT-likely patients.
        • In DVT likely patients with negative d-dimer:
          • A negative US is sufficient for ruling out DVT, consider discharge.
          • A positive US should be concerning for DVT, strongly consider treatment with anticoagulation.
        • In DVT likely patients with a positive d-dimer:
          • A positive US should be concerning for DVT, strongly consider treatment with anticoagulation.
          • A negative US is still concerning for DVT. A repeat US should be performed within 1 week for re-evaluation.

    *Moderate risk group should only undergo d-dimer testing for rule out without ultrasonography if a high-sensitivity d-dimer is being used.

    Critical Actions

    No decision rule should trump clinical gestalt. High suspicion for DVT should warrant imaging regardless of Wells score.

    The Wells’ Criteria for DVT is utilized for the workup of DVT. The presence of DVT is critical to the evaluation of possible PE, and if PE is on the differential, alternative decision aids such as the Wells PE or PERC rule should be entertained.


    Addition of the assigned points.

    Facts & Figures

    Scores ≥2 qualify patient as “High Risk” for DVT, per the derivation study.

    Evidence Appraisal

    • Initial article (Wells PS 2003) from 2003 took 1,096 outpatients with concern for DVT and randomized them into two groups after applying Wells’ Criteria for DVT. 520 were the control and had an ultrasound, 562 were tested with a d-dimer. If the dimer was positive these patients also received an US. If negative no US was performed. 16% of the control group and 15.5 percent of the test group had DVT or PE resulting in overall incidence of 15.7%.
    • Of the 520 control patients, 279 were considered DVT unlikely, and 241 were DVT likely. 16 (5.7%) of the unlikely patients had DVT or PE. In the control group overall, 6 (1.4%) patients who had been initially ruled out had a diagnosis of DVT on 3 month follow-up.
    • Of the 562 patients in the d-dimer group, 315 were considered unlikely and 247 considered likely to have DVT. 71 (28.7%) of the likely group had DVT. 38.8 percent of the unlikely group had a negative d-dimer and did not undergo further testing. 2 of these patients (0.4%) had confirmed DVT on 4 and 14 d follow-up. The negative predictive value of d-dimer was 96.1%.
    • This algorithm was then supported by Scarvelis and Wells in 2006. (Scarvelis D 2006)
    • A systematic review (Wells PS 2006) was performed in 2006 which evaluated 14 studies with 8239 patients that used the Wells score to predict risk of DVT and evaluated for incidence of DVT in association with moderate of high sensitivity d-dimer. This has been utilized by the American College of Chest physicians to provide guidelines for the evaluation of DVT.


    Dr. Phil Wells

    From the Creator

    Dr. Wells on use of his scores for MDCalc:

    The model should be applied only after a history and physical suggests that venous thromboembolism is a diagnostic possibility. it should not be applied to all patients with chest pain or dyspnea or to all patients with leg pain or swelling. This is the most common mistake made. Also, never never do the D-dimer first [before history and physical exam]. The monster in the box is that the D-dimer is done first and is positive (as it is for many patients with non-VTE conditions) and then the physician assumes that VTE is now possible and then the model is done. Do the history and physical exam first and decide if VTE is a diagnostic possibility!

    Dr. Wells on testing in medicine for MDCalc:

    The importance of Clinical pretest probability is underutilized in medicine. Recognizing the power of a simple concept, derived essentially from Bayes theorem, that discordance between the clinical PTP and the test result should raise suspicion of a false negative test (if high PTP) or false positive test (if low PTP), we sought to derive prediction rules for suspected DVT and for suspected PE. Used appropriately these rules will improve patient care.

    About the Creator

    Phil Wells, MD, MSc, is a professor and chief of the Department of Medicine at The University of Ottawa. He is also on the faculty of medicine and a senior scientist at the Ottawa Hospital Research Institute. Dr. Wells researches thromboembolism, thrombophilia and long term bleeding risk in patients on anticoagulants.

    To view Dr. Phil Wells's publications, visit PubMed

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    About the Creator
    Dr. Phil Wells
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