How do you diagnose pulmonary embolism - when is D-dimer enough vs when is CTPA needed?

1 Answer

PE Diagnosis Algorithm (ESC 2019 Guidelines): Step 1: Assess Clinical Probability (Wells Score or Geneva Score) Wells Score: - DVT symptoms: +3 - PE most likely diagnosis: +3 - HR >100: +1.5 - Immobilization/surgery in past 4 weeks: +1.5 - Previous DVT/PE: +1.5 - Haemoptysis: +1 - Cancer: +1 Interpretation: Low <2, Moderate 2-6, High >6 Step 2: Algorithmic Approach: LOW Probability (Wells <2): - D-dimer FIRST: If normal (<500 ng/mL) = PE RULED OUT, no imaging needed - If elevated D-dimer = proceed to CTPA MODERATE Probability (Wells 2-6): - D-dimer: If normal = PE ruled out - If elevated = CTPA HIGH Probability (Wells >6) or Hemodynamically Unstable: - Go DIRECTLY to CTPA (skip D-dimer - will be elevated regardless) For your patient: Wells score = 4 (moderate), D-dimer elevated = CTPA INDICATED CTPA vs VQ Scan: - CTPA: Preferred (faster, diagnoses alternative pathology, widely available) - VQ Scan: Use if renal impairment, contrast allergy, pregnancy (less radiation to fetus), or normal CXR with low pre-test probability Massive PE (hemodynamic compromise): Bedside echo for RV strain, immediate systemic thrombolysis if confirmed