Management of Suspected Deep Venous Thrombosis in Outpatients by Using Clinical Assessment and D-Dimer Testing

jective testing is required to confirm or refute the diagnosis. Objective: To determine whether the combination of a low clinical suspicion and a normal D-dimer result rules out deep venous thrombosis. Design: Prospective cohort study. Setting: Three tertiary care hospitals in Canada. Patients: 445 outpatients with a suspected first episode of deep venous thrombosis. Interventions: Patients were categorized as having low, moder-ate, or high pretest probability of thrombosis and underwent whole-blood D-dimer testing. Patients with a low pretest proba-bility and a negative result on the D-dimer test had no further diagnostic testing and received no anticoagulant therapy. Addi-tional diagnostic testing was done in all other patients. Measurements: Venous thromboembolic events during 3-mont