Wells' Criteria for DVT Probability

The Wells Score for Deep Vein Thrombosis (DVT), often referred to as Wells-DVT, is a widely validated clinical risk assessment tool used to estimate the pre-test probability of a patient having DVT in the lower limbs. Its purpose is to stratify patients, helping to guide the decision on the need for further diagnostic tests, such as D-dimer or Doppler ultrasonography.

The score operates on an additive scoring system, where +1 point is assigned for each of the following criteria: active cancer (treatment within the last 6 months or palliative); paralysis, paresis, or recent plaster immobilization of the lower limb; recent bed rest for more than 3 days or major surgery within the last 12 weeks; localized tenderness along the distribution of the deep venous system; swelling of the entire leg; calf swelling (circumference more than 3 cm greater than the asymptomatic leg, measured 10 cm below the tibial tuberosity); pitting edema confined to the symptomatic leg; and presence of collateral superficial veins (non-varicose). Crucially, -2 points are subtracted if an alternative diagnosis is considered as likely or more likely than DVT.

The total score classifies the risk: in a three-tier approach, 0 or fewer points indicate low probability, 1-2 points indicate moderate probability, and 3 or more points indicate high probability. More common in modern practice, especially in algorithms that include D-dimer, is the two-tier classification: "DVT Unlikely" (score of 1 or less) or "DVT Likely" (score of 2 or more).