What is the most appropriate next step in evaluating a patient with sudden chest pain, difficulty breathing, and tachycardia, with a history of obesity and recent immobility, for pulmonary embolism (PE)?

Calculating Clinical Probability Score is the Most Appropriate Next Step

The most appropriate next step is to calculate a validated clinical prediction rule (Wells score or revised Geneva score) to stratify this patient's pretest probability of pulmonary embolism, which will then guide whether to proceed with D-dimer testing or imaging. 1, 2

Why Risk Stratification Must Come First

This patient cannot be evaluated with any diagnostic test until you establish his pretest probability of PE using a structured approach. 1 The American College of Physicians explicitly states that clinicians must use validated clinical prediction rules to estimate pretest probability before ordering any diagnostic tests. 1

Applying the Wells Score to This Patient

Calculate the Wells score by assigning points for the following criteria present in this case: 2, 3

• Clinical signs of DVT: 0 points (no calf pain or leg swelling reported) 2
• PE as likely or more likely than alternative diagnosis: Potentially 3 points (sudden onset chest pain and dyspnea with clear risk factors) 2
• Heart rate >100 bpm: 1.5 points (HR = 102 bpm) 2
• Immobilization ≥3 days or surgery within 4 weeks: 1.5 points (recent long car ride qualifies as immobilization) 2, 3
• Previous DVT/PE: 0 points (none reported) 2
• Hemoptysis: 0 points (absent) 2
• Malignancy: 0 points (none reported) 2

This patient likely scores 3-6 points, placing him in the intermediate probability category (Wells score 2-6 points = ~30% PE prevalence). 2

Why PERC Criteria Cannot Be Applied Here

The Pulmonary Embolism Rule-Out Criteria (PERC) would be inappropriate for this patient because he fails multiple criteria: 2, 4

• Age >50 years (patient is 58 years old) 2
• Heart rate ≥100 bpm (HR = 102 bpm) 2
• Oxygen saturation ≤94% (SaO2 = 92%) 2

PERC can only be applied when ALL eight criteria are met AND the patient has low pretest probability (<15%). 1, 2 This patient fails at least three PERC criteria, mandating further diagnostic evaluation. 2

The Algorithmic Pathway After Risk Stratification

For Intermediate Pretest Probability (Most Likely Scenario):

Obtain high-sensitivity D-dimer testing as the initial diagnostic test. 1, 5 The American College of Physicians explicitly recommends against using imaging studies as the initial test in patients with intermediate pretest probability. 1

• If D-dimer is negative using age-adjusted cutoff (age × 10 ng/mL = 500 ng/mL for this 50-year-old patient), PE is excluded with >97% sensitivity. 1, 2
• If D-dimer is positive, proceed to CT pulmonary angiography (CTPA). 1, 5

If High Pretest Probability (Wells Score >6):

Proceed directly to CTPA without D-dimer testing. 1, 2 In high-risk patients, a negative D-dimer will not obviate the need for imaging, making the test unnecessary. 2, 5

Critical Pitfalls to Avoid

Do not order CTPA as the initial test without first establishing pretest probability and considering D-dimer. 5 This leads to overutilization of CT imaging, unnecessary radiation exposure (particularly concerning given increasing cancer risk), and detection of clinically insignificant subsegmental emboli. 1, 5

Do not skip the formal risk stratification step. 1 While clinical gestalt performs equally well as formal prediction rules when used by experienced clinicians (sensitivity 97%, specificity 22%), structured scoring ensures consistency and reduces diagnostic errors, particularly for less experienced providers. 2

Do not apply PERC criteria to patients with moderate or high clinical probability. 2 PERC was specifically designed for emergency department patients with already-established low clinical probability (<15% pretest probability). 2

Why This Approach Optimizes Patient Outcomes

Using validated clinical prediction rules followed by selective D-dimer testing can safely avoid imaging in 30-32% of patients with suspected PE. 5 This algorithmic approach:

• Reduces radiation exposure and associated cancer risk 1
• Decreases contrast-related complications 1
• Avoids detection of clinically insignificant findings requiring unnecessary follow-up 1
• Maintains diagnostic safety with negative predictive values >98% 2, 3

The evidence consistently demonstrates that this structured approach does not compromise mortality or morbidity outcomes while significantly reducing healthcare costs and patient harm from unnecessary testing. 1, 5