What is the recommended approach for diagnosing and treating a patient with a suspected pulmonary embolism (PE) using a scoring system like the Wells' score or Geneva score?

Recommended Approach for Diagnosing Suspected Pulmonary Embolism Using Clinical Scoring Systems

Use the Wells score as your primary clinical prediction rule for risk stratification of suspected PE, as it demonstrates superior accuracy compared to the Geneva score, and combine it with D-dimer testing in low-probability patients to safely exclude PE without imaging. 1, 2

Initial Clinical Assessment and Risk Stratification

All patients with suspected PE must have their clinical probability formally assessed and documented before any testing. 3 The Wells score is the preferred clinical decision rule based on its superior performance, with an area under the ROC curve of 0.85 compared to 0.76 for the simplified revised Geneva score. 2

Wells Score Application (Three-Level Interpretation)

Calculate the Wells score using these variables 1:

• Clinical signs/symptoms of DVT (3 points)
• PE is #1 diagnosis or equally likely (3 points)
• Heart rate >100 bpm (1.5 points)
• Immobilization ≥3 days or surgery in previous 4 weeks (1.5 points)
• Previous DVT/PE (1.5 points)
• Hemoptysis (1 point)
• Malignancy (1 point)

Risk stratification based on Wells score 1, 4:

• Low probability (0-1 points): PE prevalence 3.6% - proceed to D-dimer
• Moderate probability (2-6 points): PE prevalence 20.5% - proceed to D-dimer
• High probability (>6 points): PE prevalence 66.7% - proceed directly to CT pulmonary angiography (CTPA)

Alternative Two-Level Wells Score Interpretation

For simplified decision-making 1:

• PE unlikely (0-4 points): PE prevalence 7.8% - D-dimer can safely exclude PE
• PE likely (>4 points): PE prevalence 40.7% - proceed directly to imaging

Diagnostic Algorithm

Step 1: Low or Moderate Probability (Wells ≤6)

Order high-sensitivity D-dimer testing 3:

• If D-dimer <500 ng/mL: PE is excluded, no further testing needed. The negative predictive value is 99.5% when combined with low clinical probability. 1
• If D-dimer ≥500 ng/mL: Proceed to CTPA for diagnostic confirmation 3

Critical caveat: D-dimer should never be ordered in high-risk patients who require immediate imaging. 3 In the Wells validation study, only 1 of 437 patients with low probability and negative D-dimer developed PE during follow-up. 1

Step 2: High Probability (Wells >6)

Proceed directly to CTPA without D-dimer testing 3:

• Imaging should be performed within 24 hours for non-massive PE 3
• Within 1 hour for massive PE (hemodynamic instability) 3

Step 3: Immediate Anticoagulation Decision

Start therapeutic anticoagulation immediately in intermediate or high probability patients before imaging confirmation 3:

• Weight-based unfractionated heparin: 80 units/kg bolus, then 18 units/kg/hour infusion 3
• Target aPTT 1.5-2.5 times control (45-75 seconds) 1
• Delaying anticoagulation while awaiting diagnostic confirmation significantly increases mortality 3

Treatment Based on Imaging Results

If CTPA Confirms PE

Continue therapeutic anticoagulation 1, 3:

• Maintain heparin infusion with aPTT monitoring at 4-6 hours after bolus, 6-10 hours after dose changes, then daily 1
• Start warfarin 5-10 mg daily for 2 days, overlap with heparin for minimum 5 days 1
• Discontinue heparin when INR ≥2.0 for 24 hours 1
• Target INR 2.0-3.0 1

For hemodynamically unstable PE (massive PE), consider thrombolysis 1, 3:

• rtPA: 100 mg over 2 hours 1
• Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone) 1

If CTPA is Negative

A good quality negative CTPA excludes PE and requires no further investigation or treatment 3

Important Clinical Pitfalls

PE is easily missed in these populations 1, 3:

• Patients with severe pre-existing cardiorespiratory disease
• Elderly patients
• When the only symptom is isolated dyspnea without chest pain or hemoptysis

Classic presentations to recognize 1, 3:

• Sudden collapse with raised jugular venous pressure
• Pulmonary hemorrhage syndrome (pleuritic pain and/or hemoptysis)
• Isolated dyspnea (no cough/sputum/chest pain)
• Most patients are breathless and/or tachypneic (respiratory rate >20/min) 1

PE is rare if age <40 with no risk factors 1

Why Wells Score Over Geneva Score

The Wells score outperforms the Geneva score in multiple studies 2, 5:

• Higher area under ROC curve (0.85 vs 0.76) 2
• Better discrimination in high-risk patients 1
• More accurate prevalence prediction across all risk categories 5

Important limitation: Both Wells and Geneva scores have not been validated and are unreliable predictors in critically ill patients, where the Wells score had only 40% sensitivity and the Geneva score performed even worse. 6 In ICU patients, maintain a lower threshold for proceeding directly to imaging regardless of score.