Wells Score for DVT Calculator
Score the 2-level Wells model for deep vein thrombosis: nine risk items worth 1 point each and an alternative diagnosis that subtracts 2.
What it does
A swollen, tender leg has many possible causes, and deep vein thrombosis is the one that punishes a missed diagnosis. The Wells score is the front door of the workup: a short list of findings that a clinician can check at the bedside to sort a suspected DVT into likely or unlikely.
The 2-level version scores nine items at 1 point each, from active cancer and recent immobilization to calf swelling and collateral veins, then subtracts 2 points when another diagnosis explains the leg at least as well as DVT does.
The total splits at 2: scores of 2 or more mean DVT is likely, and scores of 1 or less mean it is unlikely. Each branch leads to a different test path, which is the whole point of the score. It is a sorting tool, not a diagnosis.
The 2003 Wells study in the New England Journal of Medicine set out the model and the testing path that NICE later adopted: imaging without delay for the likely group, and a D-dimer first for the unlikely group.
This page scores the 2-level model exactly as NICE NG158 lists it, walks through a worked example, and collects the questions patients and students ask most.
How to use
- Answer each of the nine clinical items: cancer, paralysis or cast, immobility or surgery, tenderness, leg swelling, calf measurement, pitting edema, collateral veins, and prior DVT.
- Answer the final question: is another diagnosis at least as likely as DVT? That removes 2 points.
- Read the total: 2 or more is likely, 1 or less is unlikely.
- Match the likelihood to the usual next step, then hand the score to the clinical team.
- Remember the score in the setting where it was validated: an outpatient or emergency evaluation of a first suspected DVT.
Formula
- Items
- Cancer, paralysis or cast, bedridden or surgery, tenderness, whole-leg swelling, calf difference of 3 cm, pitting edema, collateral veins, prior DVT.
- Alt dx
- Alternative diagnosis at least as likely, which subtracts 2 points.
The subtraction matters: three points from symptoms drop to 1 with a convincing alternative diagnosis, flipping likely to unlikely and changing the test path. NICE NG158 uses this 2-level form and adds the testing rule: ultrasound within 4 hours for likely, D-dimer for unlikely. A negative D-dimer in the unlikely group safely avoids imaging in most adults.
Worked example
Example: calf swelling with tenderness
Tenderness and a 3 cm calf difference, no other items (defaults).
- Tenderness along the vein course: 1 point.
- Calf swelling 3 cm or more: 1 point.
- All other items including the alternative diagnosis: 0.
- Total: 2 of a possible 7 (9 minus the 2-point subtraction).
- Score of 2 means DVT is likely, so the usual path is a proximal leg vein ultrasound within 4 hours.
Reference table
| Item | Points |
|---|---|
| Active cancer | +1 |
| Paralysis, paresis, or recent cast | +1 |
| Bedridden 3 days or major surgery within 12 weeks | +1 |
| Tenderness along the deep vein course | +1 |
| Entire leg swollen | +1 |
| Calf swelling 3 cm or more | +1 |
| Pitting edema, symptomatic leg | +1 |
| Collateral superficial veins | +1 |
| Previous DVT | +1 |
| Alternative diagnosis at least as likely | -2 |
Limits
- For suspected first DVT. Recurrent DVT, pregnancy, and anticoagulant use change the picture.
- The prior DVT item covers a previous clot on either side.
- The score was built for outpatient and emergency use, not for inpatients with many overlapping conditions.
- It does not replace imaging or D-dimer testing; it only chooses which path comes first.
Common mistakes
- Forgetting the minus 2 for a convincing alternative diagnosis and inflating the score.
- Measuring the calf at the wrong height; the reference point is 10 cm below the tibial tuberosity.
- Using the score for a patient already on anticoagulation, where it was not validated.
- Counting both legs when only the symptomatic leg counts.
- Treating a likely score as a diagnosis instead of a trigger for imaging.
Try it yourself
Quick checks. Answers sit tucked under each question.
Active cancer, entire leg swollen, no alternative diagnosis. Score and path?
2 points, so DVT likely; proximal leg vein ultrasound within 4 hours.
Calf swelling only, but a muscle tear explains the leg at least as well.
1 - 2 = -1, so DVT unlikely; start with a D-dimer.
All nine items present, no alternative diagnosis.
9 points, DVT likely; imaging without delay.
Questions
What is the difference between the 2-level and 3-level Wells score?
Both use the same ten items. The 2-level version splits at 2 into likely and unlikely; the 3-level version splits into low, moderate, and high with different cut points. NICE uses the 2-level form.
Does a score of 2 or more mean I have a clot?
No. It means the probability is high enough that imaging should not wait. Ultrasound confirms or rules out the clot.
Can the score be negative?
Yes, down to -2, when the alternative diagnosis item is the only one chosen. Negative still sits in the unlikely band.
Is the D-dimer always needed when the score is low?
It is the usual first step in the unlikely group, with imaging reserved for positive results. Some situations skip straight to imaging.
Does pregnancy change things?
Yes. Pregnancy alters both D-dimer results and imaging choices, and pregnancy-specific pathways replace the standard score.
What if I have had a DVT before?
Previous DVT adds 1 point, and any new swelling on that side is also harder to interpret on ultrasound, so clinicians often move faster to imaging.
Sources
- NICE guideline NG158: venous thromboembolic diseases, the 2-level DVT Wells score
- Wells et al, Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis, NEJM 2003