Non-invasive diagnosis of venous thromboembolism in outpatients

Background We designed a simple and integrated diagnostic algorithm for acu te venous thromboembolism based on clinical probability assessment of deep- vein thrombosis (DVT) or pulmonary embolism (PE), plasma D-dimer measuremen t, lower-limb venous compression ultrasonography, and lung scan to reduce t he need for phlebography and pulmonary angiography. Methods 918 consecutive patients presenting at the emergency ward of the Ge neva University Hospital, Geneva, Switzerland, and Hopital Saint-Luc, Montr eal, Canada, with clinically suspected venous thromboembolism were entered into a sequential diagnostic protocol. Patients in whom venous thromboembol ism was deemed absent were not given anticoagulants and were followed up fo r 3 months. Findings A normal D-dimer concentration (<500 mu g/L by a rapid ELISA) rule d out venous thromboembolism in 286 (31%) members of the study cohort, wher eas DVT by ultrasonography established the diagnosis in 157 (17%). Lung sca n was diagnostic in 80 (9%) of the remaining patients. Venous thromboemboli sm was also deemed absent in patients with low to intermediate clinical pro bability of DVT and a normal venous ultrasonography (236 [26%] patients), a nd in patients with a low clinical probability of PE and a non-diagnostic r esult on lung scan (107 [12%] patients). Pulmonary angiography and phlebogr aphy were done in only 50 (5%) and 2 (<1%) of the patients, respectively. H ence, a non-invasive diagnosis was possible in 866 (94%) members of the ent ire cohort. The 3-month thromboembolic risk in patients not given anticoagu lants, based on the results of the diagnostic protocol, was 1.8% (95% CI 0. 9-3.1). Interpretation A diagnostic strategy combining clinical assessment, D-dimer , ultrasonography, and lung scan gave a non-invasive diagnosis in the vast majority of outpatients with suspected venous thromboembolism, and appeared to be safe.