Using clinical evaluation and lung scan to rule out suspected pulmonary embolism - Is it a valid option in patients with normal results of lower-limbvenous compression ultrasonography?

Background: In patients with a low clinical probability of pulmonary emboli sm (PE) and a nondiagnostic lung scan, the prevalence of PE is theoreticall y very low. We assessed the safety and usefulness of this association for r uling out PE. Methods: We analyzed data from 2 consecutive cohort management studies perf ormed in 2 university hospitals (Geneva University Hospital, Geneva, Switze rland, and Hopital Saint-Luc, Montreal, Quebec),which enrolled 1034 consecu tive patients who came to the emergency department with clinically suspecte d PE. All patients were submitted to a sequential diagnostic protocol of lu ng scan, D-dimer testing, lower-limb venous compression ultra-sonography (U S), and pulmonary angiography in case of inconclusive results of noninvasiv e workup. Results: The prevalence of PE was 27.6%. Empirical assessment was accurate for identifying patients with a low likelihood of PE (8.2% prevalence of PE in the low clinical probability category). One hundred eighty patients had a low clinical probability of PE and a nondiagnostic lung scan. Among thes e patients, US showed deep vein thrombosis in 5. Hence, PE could be ruled o ut by a low clinical probability, a nondiagnostic lung scan, and a normal U S in 175 patients (21.5%). The 3-month thromboembolic risk in these patient s was low (1.746; 95% confidence interval, 0.4%-4.9%). Conclusions: Anticoagulant treatment could be safely withheld in patients w ith a low clinical probability of PE and a nondiagnostic lung scan, provide d that the US is normal. This combination of findings avoided pulmonary ang iography in 21.5% of patients with suspected PE in this series.