Wells Score for Pulmonary Embolism

Wells PE Calculator

Check all that apply to the current presentation.

Clinical signs/symptoms of DVT (leg swelling, pain on deep vein palpation) +3.0

PE is #1 diagnosis OR equally likely as alternative +3.0

Heart rate >100 bpm +1.5

Immobilisation (≥3 consecutive days) or surgery in previous 4 weeks +1.5

Previously documented DVT or PE (objectively diagnosed) +1.5

Haemoptysis +1.0

Malignancy (on treatment, treated in last 6 months, or palliative) +1.0

PE Unlikely

2-Level

Low

3-Level

Score ≤4: Send D-dimer. Negative D-dimer excludes PE.

Score Components

3.0 pts	Clinical signs and symptoms of DVT (leg swelling, pain on deep palpation of leg veins)
3.0 pts	PE is the #1 diagnosis, or equally likely as an alternative diagnosis
1.5 pts	Heart rate >100 beats per minute
1.5 pts	Immobilisation ≥3 consecutive days OR surgery within 4 weeks requiring general or regional anaesthesia
1.5 pts	Previous objectively diagnosed DVT or PE
1.0 pt	Haemoptysis
1.0 pt	Malignancy: on treatment, treated in last 6 months, or receiving palliative care

Maximum score = 12.5 points. The "PE as most likely diagnosis" criterion is intentionally subjective and requires clinical judgement.

Two-Level Interpretation (Recommended)

Score	Category	PE Prevalence	Recommended Action
≤4	PE Unlikely	~10%	D-dimer test. Negative D-dimer: PE excluded. Positive D-dimer: proceed to CTPA.
>4	PE Likely	~35%	CTPA directly (do not wait for D-dimer). Start anticoagulation if delay expected.

Two-level model validated by Christopher study (Ann Intern Med 2006) and YEARS algorithm. Preferred approach in most guidelines.

Three-Level Interpretation (Original)

Score	Category	PE Prevalence	Recommended Action
0–1	Low Probability	~3.4%	D-dimer (high-sensitivity). Negative: PE excluded. Positive: CTPA.
2–6	Moderate Probability	~27.8%	D-dimer. Negative: PE excluded. Positive: CTPA.
≥7	High Probability	~78.4%	CTPA directly. Start empirical anticoagulation if CTPA is delayed.

Clinical Application

Recommended two-level pathway:
Score ≤4 (PE Unlikely): High-sensitivity D-dimer → Negative = PE excluded (no further imaging needed) → Positive = CTPA

Score >4 (PE Likely): CTPA directly (no D-dimer required)

D-dimer caveats: D-dimer has high sensitivity but low specificity. It is elevated in many conditions (infection, malignancy, pregnancy, post-surgery, elderly patients). A negative D-dimer effectively excludes PE only when pre-test probability is low or intermediate. D-dimer is not useful when pre-test probability is high — a negative result would not be believed, and a positive result is non-diagnostic.
CTPA: CT pulmonary angiography is the diagnostic gold standard for PE. It directly visualises filling defects in the pulmonary vasculature. If CTPA is unavailable or the patient has renal impairment/contrast allergy, V/Q scanning is the alternative.
Empirical anticoagulation: If there is a high clinical suspicion of PE and a delay of >4 hours is expected before CTPA, therapeutic anticoagulation (LMWH or unfractionated heparin) should be started immediately while awaiting imaging confirmation.
Pregnancy: The standard Wells score has not been specifically validated in pregnancy. For pregnant patients with suspected PE, compression ultrasonography for DVT is the first step. If negative, V/Q scanning is preferred over CTPA to avoid fetal thyroid irradiation.
PERC rule: In very low-risk patients (clinical gestalt), the Pulmonary Embolism Rule-Out Criteria (PERC) may be applied before even calculating the Wells score. If all 8 PERC criteria are met, no further testing is needed.

References

Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: Increasing the models utility with the SimpliRED D-dimer. Thromb Haemost. 2000;83(3):416–420.
Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and D-dimer. Ann Intern Med. 2001;135(2):98–107.
van Belle A, Büller HR, Huisman MV, et al. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172–179.