Withholding anticoagulation after a negative result on duplex ultrasonography for suspected symptomatic deep venous thrombosis

Background: Negative results on simplified compression ultrasonography cannot rule out symptomatic deep venous thrombosis (DVT) without further testing, such as repeated ultrasonography several days later. Repeated testing is costly and inconvenient, and patients are sometimes less likely to return for follow-up tests. Objective: To determine the rate of venous thromboembolism when anticoagulation is withheld in patients with symptoms of DVT of the leg after negative results on a single examination with comprehensive duplex ultrasonography. Design: Prospective clinical cohort study. Setting: Peripheral vascular laboratory of a tertiary care academic hospital. Patients: 445 consecutive patients in whom a first episode of symptomatic DVT was suspected. Intervention: The researchers examined the entire leg with comprehensive duplex ultrasonography, using compression and Doppler techniques. Anticoagulation was withheld from the group with negative results. Patients were observed for thromboembolic events for 3 months. Measurements: All patients who had new or progressive symptoms or signs of venous thromboembolism during follow-up underwent objective testing. Results: Comprehensive duplex ultrasonography yielded normal results in 384 patients (86.3%) and showed DVT in 61 patients (13.7%). Nineteen cases of DVT (31.1%) were isolated to the deep veins of the calf. Nine patients in the negative cohort (2.3%) were excluded from analysis because they received anticoagulation for reasons unrelated to venous thromboembolism. Three of 375 patients (0.80% [95% CI, 0.16% to 2.33%]) in the normal cohort had symptomatic venous thrombosis during the 3-month follow-up. All 384 patients in the negative cohort completed follow-up. Limitations: The study was conducted at a single tertiary care center by a peripheral vascular staff with substantial experience in duplex ultrasonography, which may limit the applicability of the results to other institutions. Pregnant patients were excluded. Conclusions: It is safe to withhold anticoagulation after negative results on comprehensive duplex ultrasonography in nonpregnant patients with a suspected first episode of symptomatic DVT of the leg. New or progressive symptoms should prompt further testing.