Wells’ criteria for pulmonary embolism (PE)

Wells’ criteria for pulmonary embolism is a clinical prediction rule used to estimate the pre-test probability of PE in patients presenting with symptoms suggestive of venous thromboembolism.

The score supports diagnostic decision-making by stratifying patients into likelihood categories and guiding the appropriate use of D-dimer testing and imaging.

Clinical context and use

Wells’ criteria for PE is used in primary care, emergency departments, and hospital settings when assessing patients with symptoms such as acute onset breathlessness, pleuritic chest pain, haemoptysis, syncope, or unexplained tachycardia.

Its primary role is to estimate the probability of PE before investigation, helping clinicians decide whether PE can be ruled out using D-dimer testing or whether immediate imaging is required.

The score is most appropriate for patients with suspected acute PE and should be applied before diagnostic testing where possible.

Points are assigned for the following clinical features:

• Clinical signs of deep vein thrombosis, such as leg swelling and pain with palpation, score 3 points.

• Pulmonary embolism judged to be the most likely diagnosis scores 3 points.

• Heart rate greater than 100 beats per minute scores 1.5 points.

• Immobilisation for more than 3 days or surgery within the previous 4 weeks scores 1.5 points.

• Previous documented DVT or PE scores 1.5 points.

• Haemoptysis scores 1 point.

• Active cancer, defined as treatment ongoing, within the previous 6 months, or palliative, scores 1 point.

The total score reflects the estimated clinical probability of PE.

Wells’ criteria for PE can be interpreted using either a three-level or two-level model.

In the traditional three-level model:

• A score of 0–1 indicates low probability.

• A score of 2–6 indicates moderate probability.

• A score of more than 6 indicates high probability.

In the simplified two-level model, which is commonly used in UK practice:

• A score of 4 points or fewer indicates PE unlikely.

• A score of more than 4 points indicates PE likely.

Local diagnostic pathways should be followed when applying either model.

Wells’ criteria is typically used as the first step in a structured PE assessment pathway.

In patients classified as PE unlikely, a negative D-dimer test may be sufficient to safely exclude PE without the need for imaging. In patients classified as PE likely, or with a positive D-dimer, definitive imaging such as CT pulmonary angiography is usually indicated.

The score helps reduce unnecessary imaging while maintaining diagnostic safety.

Wells’ criteria for PE was developed and validated in outpatient and emergency department populations and has been shown to safely reduce imaging when combined with D-dimer testing.

It remains one of the most widely used clinical prediction rules for suspected PE and is incorporated into national and international diagnostic guidelines.

Wells’ criteria does not diagnose PE and should not be used in isolation.

Its accuracy may be reduced in certain populations, including:

• Hospital inpatients.

• Pregnant patients.

• Patients already receiving anticoagulation.

• Patients with recurrent PE.

Clinical judgement remains essential, particularly in patients who are haemodynamically unstable or have red flag features such as syncope, hypoxia, or circulatory compromise.

Using Wells’ criteria provides a structured and reproducible approach to assessing suspected PE. Documenting the score can support clinical reasoning, guide investigation, and improve communication between clinicians.

Clear safety-netting and escalation advice should be provided, particularly when PE is considered unlikely but symptoms persist or worsen.