Diagnosis of pulmonary embolism in patients with proximal deep vein thrombosis: specificity of symptoms and perfusion defects at baseline and during anticoagulant therapy.

To determine the specificity of pulmonary embolism (PE) symptoms and lung scan perfusion defects in patients with deep vein thrombosis (DVT), we analyzed data on 400 patients with phlebography-proven proximal DVT included in a prospective trial. As the incidence of PE during anticoagulant therapy was the main outcome measure of the trial, all patients underwent lung scanning and/or pulmonary angiography within 48 h of inclusion, and then whenever PE was suspected. Angiography was recommended in patients with nondiagnostic lung scan. At baseline, the presence or absence of PE could be ascertained in 350 patients (87.5%), and 197 (56%) had PE. Sensitivity and specificity of symptoms for PE were 74 and 67%, respectively. Among 37 patients with symptoms and nondiagnostic lung scan, only 8 (22%) had PE at angiography. During anticoagulant therapy (3 mo), there were 29 events suspicious for PE, mostly (53%) within 2 wk of inclusion. Repeated perfusion studies with comparison to baseline tests excluded PE in 21 cases. Cumulated 3-mo risks of suspected and confirmed on-treatment PE were 6.8% (95% CI, 5.4- 8.2%) and 2.0% (95% CI, 0.6-3.4%) respectively. Even in patients with known proximal DVT, PE symptoms are unspecific and careful imaging studies are needed for diagnosis, both at baseline and during anticoagulant therapy.