Wells criteria for deep venous thrombosis

Last revised by Henry Knipe on 03 Nov 2018

Wells criteria for deep venous thrombosis is a risk stratification score and clinical decision rule to estimate the pretest probability for acute deep venous thrombosis (DVT). It is intended to be combined with noninvasive diagnostic tests (e.g. ultrasound or D-dimer) for suspected cases. D-dimer may be more useful in those with a low Wells score as those with higher will likely be referred for ultrasound regardless and D-dimer result will therefore not change management.


A Wells score is calculated with patients scoring +1 point for each of the below criteria 5:

  • active cancer (ongoing treatment/ treatment within last 6 months, or palliative)
  • paralysis, paresis, or recent plaster immobilization of the legs
  • recently bedridden for ≥3 days, or major surgery within the last 12 weeks requiring general or local anesthetics
  • localized tenderness along the distribution of the deep venous system
  • entire leg swelling
  • calf swelling >3 cm compared with the asymptomatic leg (measured at 10 cm below the tibial tuberosity)
  • pitting edema (greater than on the asymptomatic leg)
  • collateral superficial veins (non-varicose)
  • previously documented DVT

Two points are subtracted if an alternative diagnosis is more likely than DVT (e.g. muscular tear, cellulitis, etc).

DVT is considered likely in patients with a Wells score of 2 or above and unlikely in patients with a score of less than 2.


  • there is controversy as to whether the score is effective for inpatients 2
  • in patients with a history of cancer, the combination of the Wells score and D-dimer may not be appropriate for evaluation 3
  • pretest clinical probability with the Wells score may have a low diagnostic accuracy for isolated distal DVT 4​

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