OBJECTIVE: Our objective was to determine the prevalence of deep vein thrombosis in symptomatic patients and its distribution based on the assessment of prior clinical probability. We evaluated whether repeated sonography is necessary in patients with either intermediate or high clinical probability for deep vein thrombosis after an initial examination with negative findings. SUBJECTS AND METHODS: We prospectively evaluated 438 consecutive patients with clinical suggestion of deep vein thrombosis of the lower limbs, classified according to the prior clinical probability (high, intermediate, low). Sonography with positive findings was diagnostic for deep vein thrombosis. Negative findings in low-risk patients excluded thrombosis. Patients with intermediate or high clinical risk whose initial sonographic examination showed negative findings underwent a second examination after 1 week. RESULTS: Of the 438 patients with clinical symptoms, 112 patients (26%) had positive findings on sonography, and 326 (74%) had negative findings. Of the 202 intermediate- and high-risk patients with negative initial sonography, 140 patients underwent a single follow-up sonographic examination 1 week later. In three cases, findings were positive for deep vein thrombosis. Two other patients developed pulmonary embolism. Sonographic follow-up increased the detection of deep vein thrombosis in the patients with intermediate or high probability from 32.5% to 33.5%; the prevalence of thromboembolic disease in this group was 34%. CONCLUSION: The prevalence of deep vein thrombosis studied by sonography in the patients with intermediate or high clinical risk was 33.5%. Initial sonography revealed a 32.5% prevalence, and a second examination 1 week later detected an additional 1%. Sonography did not reveal 0.5% of thromboembolic events. Our results do not justify a routine second scanning at 1 week.
OBJECTIVE: Our objective was to determine the prevalence of deep vein thrombosis in symptomatic patients and its distribution based on the assessment of prior clinical probability. We evaluated whether repeated sonography is necessary in patients with either intermediate or high clinical probability for deep vein thrombosis after an initial examination with negative findings. SUBJECTS AND METHODS: We prospectively evaluated 438 consecutive patients with clinical suggestion of deep vein thrombosis of the lower limbs, classified according to the prior clinical probability (high, intermediate, low). Sonography with positive findings was diagnostic for deep vein thrombosis. Negative findings in low-risk patients excluded thrombosis. Patients with intermediate or high clinical risk whose initial sonographic examination showed negative findings underwent a second examination after 1 week. RESULTS: Of the 438 patients with clinical symptoms, 112 patients (26%) had positive findings on sonography, and 326 (74%) had negative findings. Of the 202 intermediate- and high-risk patients with negative initial sonography, 140 patients underwent a single follow-up sonographic examination 1 week later. In three cases, findings were positive for deep vein thrombosis. Two other patients developed pulmonary embolism. Sonographic follow-up increased the detection of deep vein thrombosis in the patients with intermediate or high probability from 32.5% to 33.5%; the prevalence of thromboembolic disease in this group was 34%. CONCLUSION: The prevalence of deep vein thrombosis studied by sonography in the patients with intermediate or high clinical risk was 33.5%. Initial sonography revealed a 32.5% prevalence, and a second examination 1 week later detected an additional 1%. Sonography did not reveal 0.5% of thromboembolic events. Our results do not justify a routine second scanning at 1 week.