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Calculate the Wells score to estimate the probability of pulmonary embolism (PE) and guide diagnostic workup.
Wells Score
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Two-Tier Classification
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| Wells Score | Classification | PE Probability | Action |
|---|---|---|---|
| ≤4 | PE Unlikely | ~8% | D-dimer test |
| >4 | PE Likely | ~35% | Imaging (CTPA) |
| Wells Score | Risk Level | PE Probability |
|---|---|---|
| 0-1 | Low | 1.3% |
| 2-6 | Moderate | 16.2% |
| >6 | High | 37.5% |
The Wells score for pulmonary embolism is a clinical decision rule used to estimate the pretest probability of PE. It helps determine which patients require imaging and which can be safely evaluated with D-dimer testing alone, reducing unnecessary radiation exposure and healthcare costs.
The two-tier model (PE likely vs unlikely) is more commonly used in clinical practice. Patients with Wells score ≤4 (PE unlikely) can undergo D-dimer testing first - if negative, PE is ruled out. Patients with score >4 (PE likely) should proceed directly to CT pulmonary angiography (CTPA) without D-dimer testing.
In very low-risk patients (Wells score <2 and PERC rule negative), some guidelines suggest no further testing is needed. The PERC (Pulmonary Embolism Rule-out Criteria) includes 8 criteria - if all are absent, PE can be safely ruled out without D-dimer or imaging.
The criterion "PE is most likely diagnosis" requires clinical judgment and is the most subjective component. It should only be checked when no alternative diagnosis better explains the patient's symptoms. D-dimer sensitivity decreases with age, pregnancy, and hospitalization - age-adjusted D-dimer cutoffs improve specificity in older patients.
Use the Wells score when PE is being considered in the differential diagnosis based on symptoms like chest pain, shortness of breath, or hemoptysis. Calculate the score before ordering tests to guide appropriate diagnostic strategy.
These are separate scoring systems for different conditions. Wells PE assesses pulmonary embolism probability using different criteria than Wells DVT, which evaluates deep vein thrombosis risk. Use the appropriate score based on clinical presentation.
Low Wells score alone does not rule out PE. You must also obtain a D-dimer. Only when both Wells score is ≤4 (PE unlikely) AND D-dimer is negative can you safely exclude PE without imaging.
Clinical signs of DVT include unilateral leg swelling, warmth, erythema, or pain with palpation along the deep venous system. This criterion is worth 3 points, making it highly significant in the Wells PE score.
The two-tier model (PE likely vs unlikely) is more commonly used and better validated for guiding D-dimer vs imaging decisions. The three-tier model provides more granular risk stratification but doesn't change management significantly.
If CTPA is contraindicated (severe contrast allergy, renal failure), consider ventilation-perfusion (V/Q) scan as an alternative. Lower extremity ultrasound showing DVT can also justify anticoagulation without pulmonary imaging.
The Wells score can be used in pregnancy, but interpretation is challenging as D-dimer is often elevated physiologically. In pregnant patients with suspected PE, many proceed directly to imaging regardless of Wells score to avoid missing this serious diagnosis.
In high-probability patients (Wells >4) without contraindications, empiric anticoagulation while awaiting CTPA is reasonable if imaging cannot be obtained immediately. This decision should weigh bleeding risk against potential benefit.