Wells Score for Pulmonary Embolism Calculator

Understanding the Wells score for pulmonary embolism — concept and principle

The Wells score for pulmonary embolism (PE) estimates the pretest probability that a patient's symptoms, such as breathlessness or chest pain, are caused by a clot in the lung arteries. It helps decide whether to start with a D-dimer test or go straight to imaging such as CT pulmonary angiography.

How it is calculated

Add the points for each item present:

• Clinical signs and symptoms of DVT: 3
• PE is the most likely diagnosis (or equally likely): 3
• Heart rate above 100 beats/min: 1.5
• Immobilisation for 3 days or more, or surgery in the previous 4 weeks: 1.5
• Previous DVT or PE: 1.5
• Haemoptysis: 1
• Malignancy (on treatment, recently treated or palliative): 1

The total ranges from 0 to 12.5. Two-level model: above 4 is "PE likely", 4 or less is "PE unlikely". Three-level model: below 2 low, 2 to 6 moderate, above 6 high.

The principle

Like other clinical prediction rules, the score was built by recording features in patients with suspected PE and identifying those independently linked to a confirmed diagnosis. Larger weights go to the strongest predictors: signs of DVT, where the clot usually starts, and the clinician's judgement that PE is the leading diagnosis. The resulting probability frames how tests are read. A negative D-dimer reliably excludes PE when the probability is low, while a high probability calls for imaging regardless of D-dimer.

Worked example

1. Defaults: all seven items No.
2. Score = 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0.
3. Two-level: 0 is not above 4, so PE unlikely.
4. Three-level: 0 is below 2, so low.
5. For comparison, heart rate 110 and surgery two weeks ago give 1.5 + 1.5 = 3: unlikely on the two-level model, moderate on the three-level model.

How to read the result

With "PE unlikely", a D-dimer test is usually done next, and a normal result generally rules out PE. With "PE likely", imaging is usually performed directly. In patients judged low risk, the PERC rule may avoid even the D-dimer test.

Common mistakes

• Treating "PE is the most likely diagnosis" as automatic; it requires an honest clinical judgement and drives much of the score.
• Mixing the two-level and three-level cut-offs.
• Applying the score in pregnancy without pregnancy-specific pathways.

Frequently asked questions

Why is the PE item subjective?

Clinician gestalt adds information that the objective items miss. It also makes the score less reproducible between observers.

What is a typical next step after a high score?

Usually CT pulmonary angiography, or a ventilation-perfusion scan when CT is unsuitable.

How is it different from the Geneva score?

The revised Geneva score uses only objective items, such as age and leg pain on palpation, with no clinician-judgement item.

Sources: Wells P. S. et al., Thrombosis and Haemostasis, 2000 (derivation of the PE model) · Konstantinides S. V. et al., 2019 ESC Guidelines for acute pulmonary embolism, European Heart Journal, 2020