Emergency Medicine
Wells Score for PE
Pre-test probability of pulmonary embolism.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The Wells score for pulmonary embolism (PE) estimates the pre-test probability of PE in symptomatic patients, helping to direct D-dimer testing and imaging. It assigns points for clinical signs of DVT (3), PE being the most likely diagnosis (3), heart rate over 100 (1.5), recent immobilisation or surgery (1.5), previous DVT/PE (1.5), haemoptysis (1) and active malignancy (1). The resulting total stratifies patients by probability and underpins the PE diagnostic pathway. It can be applied as either a three-level or a two-level model.
Interpreting the result
In the three-level model a score up to 1.5 is low, 2–6 moderate and above 6 high probability. The widely used two-level approach classifies 4 or less as "PE unlikely" and more than 4 as "PE likely". In the unlikely group a negative D-dimer can exclude PE, whereas the likely group proceeds to computed tomography pulmonary angiography (CTPA). Local pathways vary, so the score guides rather than dictates the route.
Advice
A common two-level approach: ≤4 = "PE unlikely" (proceed to D-dimer); >4 = "PE likely" (proceed to CTPA). Follow your local pathway.
Worked example
A patient with clinical signs of DVT (3) in whom PE is the most likely diagnosis (3) and who has a heart rate of 110 (1.5) scores 7.5. This is "PE likely" and they should proceed to CTPA rather than relying on a D-dimer.
Pearls / pitfalls
- The two subjective items — clinical signs of DVT and "PE is the most likely diagnosis" — carry the most points and rely on clinical judgement, so apply them carefully.
- A negative D-dimer is only reassuring in the "PE unlikely" group; in the "likely" group proceed to CTPA.
- In patients already judged low risk, consider the PERC rule to avoid unnecessary D-dimer testing.
- The score estimates probability, not certainty — combine it with the clinical picture and local pathway.
Evidence & validation
Derived and validated by Wells et al. and incorporated into NICE venous thromboembolism guidance, which recommends the two-level Wells score to guide D-dimer testing and CTPA in suspected PE.
Frequently asked questions
What does "PE likely" mean for next steps?
In the two-level model a score above 4 is "PE likely", and the patient proceeds to CTPA. A D-dimer is not relied upon to exclude PE in this group.
When can a D-dimer rule out PE?
A negative D-dimer can exclude PE only when the Wells score places the patient in the "PE unlikely" group (4 or less). Higher-probability patients require imaging.
How does the Wells PE score differ from the DVT version?
They share an author and a similar logic but use different criteria, weightings and thresholds, and apply to different conditions. Use the one matching the suspected diagnosis.
What if the patient is pregnant?
The Wells score is not formally validated in pregnancy, and dedicated pregnancy pathways and imaging considerations apply. Follow local obstetric and radiology guidance.
How does PERC relate to the Wells PE score?
The PERC rule is applied only once a patient is already judged low pre-test probability. If all PERC criteria are absent, PE can be excluded without a D-dimer.
References
- Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients' probability of pulmonary embolism. Thromb Haemost. 2000;83(3):416–420.
- NICE NG158: Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. 2020.
About the creator
Wells PS et al.
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