Wells’ DVT

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Use this calculator to calculate pre-test probability of Deep Vein Thrombosis (DVT) using Wells’ Criteria.

Recent treatment for cancer (last 6 months) or current palliation
Paralysis, paresis, or cast of lower extremity
Bedridden at least 3 days in last 4 weeks or major surgery in last 12 weeks
Tenderness along deep venous system
Swelling of entire leg
Unilateral calf swelling > 3 cm compared to other side
Unilateral pitting edema
Superficial collateral veins
Prior DVT
Alternative diagnosis as or more likely than DVT

About this calculator

The diagnostic accuracy for DVT improves when the clinical probability is estimated before the use diagnostic tests. It is important to note that, when using the scoring system by itself, DVT cannot be ruled out completely in patients with a low probability score or confirmed in patients with a high probability score. However, use of such a score can help inform interpretation of subsequent diagnostic tests and reduce the need for invasive testing. For instance, patients with low clinical probability on the Wells predictive rule have a prevalence of DVT of less than 5%. In some studies, the combination of a low clinical probability and a negative d-dimer result can exclude DVT without ultrasound or further testing. Because multiple D-dimer assays are available, physicians should ensure that a proven high-sensitivity assay is available and that the test has been validated/audited in their institution.


This formula is found in: Wells PS, Anderson DR, Bormanis J, Guy F, Mitchell M, Gray L, Clement C, Robinson KS, Lewandowski B. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet 350(9094):1795-8. (1997)

A diagnostic strategy that uses the pre-test probability generated by the scoring system is available from: Wells PS, Anderson DR, Rodger M, Forgie M, Kearon C, Dreyer J, Kovacs G, Mitchell M, Lewandowski B, Kovacs MJ. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med 349:1227-35. (2003)


QxMD Hematology contributing author: Dr. Matthew Cheung, MD, SM, FRCP(C)