What is the Wells' score (Wells' score for pulmonary embolism) for assessing pulmonary embolism (PE)?

Wells Score for Pulmonary Embolism Assessment

The Wells score is the most validated and recommended clinical prediction rule for stratifying patients with suspected pulmonary embolism (PE) into risk categories, with demonstrated high accuracy in determining which patients require further diagnostic testing.1

Wells Score Components and Scoring System

The Wells score for PE consists of 7 clinical variables:

• Clinical signs and symptoms of DVT (3 points) 2
• PE is the most likely diagnosis OR alternative diagnosis is less likely than PE (3 points) 2
• Heart rate > 100 beats/min (1.5 points) 2
• Immobilization for more than 3 days or surgery in the previous 4 weeks (1.5 points) 2
• Previous DVT/PE (1.5 points) 2
• Hemoptysis (1 point) 2
• Malignancy (treatment within 6 months or palliative care) (1 point) 2

Risk Stratification and Interpretation

Traditional Interpretation (Three-Tier):

• Low risk (0-1 points): 3.6% probability of PE 2
• Intermediate risk (2-6 points): 20.5% probability of PE 2
• High risk (>6 points): 66.7% probability of PE 2

Alternative Interpretation (Two-Tier):

• PE unlikely (0-4 points): 7.8% probability of PE 2
• PE likely (>4 points): 40.7% probability of PE 2

Clinical Application and Diagnostic Algorithm

1. Calculate the Wells score for patients with suspected PE 1
2. For patients with "PE unlikely" score (≤4 points), perform D-dimer testing 1
   • If D-dimer negative: PE can be safely excluded (negative predictive value of 99.5%) 1
   • If D-dimer positive: Proceed to imaging (CT pulmonary angiography) 1
3. For patients with "PE likely" score (>4 points), proceed directly to imaging 1

Advantages of the Wells Score

• Well-validated in multiple large studies with consistent performance 1
• When combined with D-dimer testing, can safely reduce the need for CT pulmonary angiography in approximately 30% of patients 1
• Demonstrates better accuracy than the simplified revised Geneva score (AUC 0.85 vs 0.76) 3
• Shows good interrater reliability for the dichotomized score (kappa value of 0.72) 4

Age-Adjusted D-dimer Considerations

• For patients over 50 years, using age-adjusted D-dimer cutoff (age × 10 μg/L) can improve diagnostic accuracy 1
• The combination of Wells score with age-adjusted D-dimer testing has demonstrated 100% sensitivity and negative predictive value 5

Potential Limitations and Pitfalls

• Contains subjective elements, particularly the "alternative diagnosis less likely than PE" criterion, which may affect consistency 1
• Moderate interrater agreement for some components, including DVT symptoms (kappa 0.54), immobilization (kappa 0.41), and "PE more likely than alternative diagnosis" (kappa 0.5) 2
• May perform less reliably in certain populations such as pregnant women, elderly patients, or those with significant comorbidities 1

Simplified Wells Score

• A simplified version of the Wells score has been developed for easier clinical application 6
• The simplified Wells score has comparable discriminatory performance to the original score (c-statistic 0.72 vs 0.73) 6
• When combined with age-adjusted D-dimer testing, both original and simplified Wells rules show similar efficiency (30% vs 33%) and failure rates (0.8% vs 0.9%) 6
• Given its ease of use in clinical practice, the simplified Wells rule may be preferred over the original Wells rule 6