Level 1: Likely reliable evidence
D-dimer plus multidetector CT (D-dimer/CT) is as effective as D-dimer/CT plus venous compression ultrasound (US) for identifying pulmonary embolism (PE) and short-term risk of thromboembolic events in patients without PE, based on a randomized trial of 1,819 consecutive outpatients with suspected PE (Lancet. 2008;371:1343-1352). Per-protocol analysis included 1,693 patients. Prior to randomization, all patients had a clinical probability assessment using the revised Geneva score (low-to-intermediate probability in 1,643 patients, high probability in 50 patients).
The primary outcome was the three-month risk of thromboembolism in patients left untreated following exclusion of PE by the assigned diagnostic strategy. Comparing D-dimer/CT strategy vs. D-dimer/US/CT strategy, there were no significant differences in prevalence of PE in the intention-to-diagnose population (20.6% vs. 20.6%) or in a per-protocol analysis (21.5% vs. 20.7%). The three-month risk of venous thromboembolism among 1,276 patients without PE and not treated with anticoagulants was 0.3% (two cases) vs. 0.3% (two cases) (not significant). The rate of all-cause mortality was 2.7% vs. 4.5% in per-protocol analysis. There were no differences in adverse events between groups.