Background: Ultrasonography using vein compression accurately detects proximal deep venous thrombosis in symptomatic outpatients. Repeated testing is required for patients with normal results at presentation, but the optimal management of such patients is uncertain.
Objective: To test the safety of withholding anticoagulation in outpatients suspected of having first-episode deep venous thrombosis who have normal results on simplified compression ultrasonography at presentation and on a single repeated test done 5 to 7 days later.
Design: Prospective cohort study.
Setting: Noninvasive vascular laboratories at a university teaching hospital and a Veterans Administration medical center.
Patients: 405 consecutive outpatients suspected of having first-episode deep venous thrombosis.
Intervention: Ultrasonography was performed at presentation. The common femoral and popliteal veins were assessed for compressibility. If the result was normal, anticoagulation was withheld and testing was repeated 5 to 7 days later. Anticoagulation was withheld from all patients whose results remained normal according to compression ultrasonography, regardless of their symptoms. The safety of this approach was tested by follow-up lasting 3 months.
Measurements: Objective testing was done during follow-up in all patients with symptoms or signs of venous thromboembolism. The outcome measure was symptomatic venous thrombosis or pulmonary embolism during follow-up, confirmed by objective testing.
Results: Ultrasonography had normal results in 335 patients (83%) and abnormal results in 70 (17%). None of the patients with normal results died of pulmonary embolism. Venous thromboembolism occurred during follow-up in 2 patients with normal ultrasonographic results (0.6% [95% CI, 0.07% to 2.14%]) and in 4 patients with abnormal results (5.7% [CI, 1.58% to 13.99%]) (P = 0.009).
Conclusions: It is safe to withhold anticoagulation in outpatients suspected of having first-episode deep venous thrombosis if results of simplified compression ultrasonography are normal at presentation and on a single repeated test done 5 to 7 days later.