Wells score for pulmonary embolism
Two-level Wells score: PE likely or unlikely, and what to do next.
What the Wells score is for
The two-level Wells score estimates how likely pulmonary embolism is before any test. NICE NG158 uses it to decide whether a patient goes straight to imaging or has a D-dimer first.
The criteria
- Clinical signs and symptoms of DVT (leg swelling and pain on palpation of the deep veins): 3
- An alternative diagnosis is less likely than PE: 3
- Heart rate above 100: 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
- Active cancer (treatment in the last 6 months or palliative): 1
Interpreting the score
- More than 4: PE likely. Arrange CTPA immediately. If it will be delayed, start interim anticoagulation unless contraindicated.
- 4 or less: PE unlikely. Send a D-dimer. If it is positive, arrange CTPA; if negative, PE is very unlikely and you should look for another cause.
In low-suspicion patients, NICE suggests the PERC rule can avoid a D-dimer altogether if all eight criteria are negative.
Worked example
A woman 10 days after a caesarean section is breathless with a heart rate of 112, and you think PE is the most likely diagnosis. Points: 3 + 1.5 + 1.5 = 6. PE likely: request CTPA and start low molecular weight heparin while waiting.
Limitations and pitfalls
- Do not do a D-dimer in "PE likely" patients: a negative result does not exclude PE when the pre-test probability is high.
- D-dimer is often raised after surgery, in pregnancy, infection, cancer and older age, so it is least useful in exactly the patients at highest risk.
- The Wells score is not validated in pregnancy. Pregnant women need a specific pathway and early senior input.
- Where CTPA is not available out of hours, anticoagulate if there is no contraindication and get a bedside echo or a leg ultrasound if a scan is delayed. A shocked patient with suspected PE is a thrombolysis decision for a senior, not a scoring exercise.
- Check kidney function before contrast; consider a V/Q scan in kidney impairment.
See pulmonary embolism, calf pain and DVT, acute breathlessness, enoxaparin, apixaban and the textbook chapter on DVT and pulmonary embolism.
Frequently asked questions
What Wells score means PE is likely?
More than 4 points on the two-level Wells score. A score of 4 or less means PE is unlikely and a D-dimer is the next test.
Should I do a D-dimer if the Wells score is high?
No. When PE is likely, go straight to CTPA. A negative D-dimer does not safely exclude PE when the pre-test probability is high.
What is the PERC rule?
Eight criteria (age under 50, heart rate under 100, SpO₂ 95% or more, no haemoptysis, no oestrogen use, no previous DVT or PE, no unilateral leg swelling, no recent surgery or trauma needing hospital care). If all are met in a low-suspicion patient, PE can be ruled out without a D-dimer.
Can I use the Wells score in pregnancy?
It is not validated in pregnancy. Pregnant women with suspected PE need a pregnancy-specific pathway, usually with leg ultrasound and imaging decided with a senior.
A calculator supports, but does not replace, clinical judgement. Check results before acting on them.