By Zencalcy Editorial TeamLast reviewed About us
The Wells score for deep vein thrombosis combines clinical findings into a pretest probability estimate. Nine items add one point each, while an alternative diagnosis judged at least as likely subtracts two. This calculator sums the selected items and reports the usual three-tier probability band.
Pretest probability of deep vein thrombosis.
Wells DVT = nine clinical items (+1 each) − alternative diagnosis at least as likely (−2)
A total of 0 or less is usually classified as unlikely, 1–2 as moderate and 3 or more as likely. The three-tier scheme is common in research, while many pathways use the two-tier version where 2 or more is likely. The score estimates pretest probability; it does not confirm or exclude thrombosis by itself.
| Symbol | Meaning |
|---|---|
| Score | Total Wells DVT points, from −2 to 9. |
| Alternative diagnosis | A diagnosis at least as likely as DVT subtracts two points. |
| Probability | The three-tier band derived from the total. |
Active cancer adds 1, tenderness along the deep veins adds 1 and prior DVT adds 1, for a total of 3 points, which is in the likely band. If an alternative diagnosis were judged at least as likely, the total would fall to 1 point and move into the moderate band. No positive items and no alternative diagnosis gives 0 points.
Pretest probability is the bridge between symptoms and testing. A score of 3 or more raises the chance that ultrasound will find a clot, which is why many pathways move straight to imaging. A score of 0 or less makes a negative D-dimer more informative, because a low-risk result plus a negative test can safely avoid imaging in many protocols. The score depends on careful examination: calf swelling measured against the other leg, tenderness along the deep venous system and a genuine judgement about alternative diagnoses. It performs less well in people who are already anticoagulated, have a history of thrombosis or present atypically. Treat the number as a structured summary of the bedside assessment, and follow the local diagnostic pathway rather than acting on the score alone.
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The item captures how strongly the overall clinical picture points away from DVT. When another diagnosis explains the findings at least as well, the probability of DVT is lower, so the score adjusts downward rather than simply staying at zero.
Blood pressure, ECG and risk scores are screening aids, not diagnoses. A single reading can be misleading; trends and proper technique matter. Scores estimate population risk and do not replace clinical assessment, anticoagulation decisions or emergency care.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Content updated: September 2026