Diagnostic Approach for Moderate Pretest Probability Pulmonary Embolism

Initial Risk Stratification

• The American College of Physicians recommends obtaining a high-sensitivity D-dimer measurement as the initial diagnostic test in patients with an intermediate pretest probability of pulmonary embolism, and imaging studies should not be used as the initial test in these patients 1

D-dimer Testing Strategy

• For patients over 50 years, an age-adjusted D-dimer cutoff calculated as age × 10 ng/mL should be used rather than the generic 500 ng/mL cutoff 1
• A D-dimer below the cutoff safely excludes pulmonary embolism without any imaging, with a high sensitivity for ruling out the condition 1, 3

Imaging When Indicated

• CT pulmonary angiography is the primary imaging modality for patients with moderate pretest probability and positive D-dimer, with high sensitivity (>95%) for segmental or larger emboli 4, 3
• If CT pulmonary angiography is contraindicated, a ventilation-perfusion scan is the first-line alternative 6, 1

Critical Pitfalls to Avoid

• D-dimer testing in moderate probability patients prevents unnecessary imaging in those with negative results, and starting with CT pulmonary angiography exposes patients to unnecessary radiation and contrast nephropathy risk 1, 6