Diagnosis of DVT: 2-Point Ultrasound plus D-Dimer Is Comparable to Whole-Leg Ultrasound
Although simpler and more readily available, the 2-point ultrasound strategy requires follow-up study in nearly one third of patients.
Two-point ultrasound for the diagnosis of deep venous thrombosis (DVT) involves evaluation of the common femoral and popliteal veins. This strategy requires that patients with normal ultrasound results and elevated D-dimer results undergo follow-up study within 1 week to detect calf DVT that would have been missed by the initial 2-point ultrasound. Newer color-coded Doppler ultrasound allows evaluation of the small and large vessels of the entire leg. Researchers compared the two strategies in a prospective, randomized study of 2098 consecutive symptomatic patients who presented to 14 centers with first episodes of suspected DVT from 2003 through 2006. Patients with normal results were followed for 3 months.
The prevalence of DVT on the initial 2-point ultrasound was 22%. Among patients with normal 2-point ultrasound findings, 31% had positive D-dimer results and underwent repeat testing at 1 week (or earlier); 5.5% had DVT. Among the whole-leg color-coded ultrasound cohort, 26% of patients had positive findings on the initial test: 77% had proximal DVT, 13% had isolated posterior tibial or peroneal DVT, and 10% had isolated muscular vein thrombosis. At 3-month follow-up, the incidence of DVT in patients who had normal findings at the initial evaluation did not differ significantly between the 2-point ultrasound and color-coded ultrasound groups (0.9% vs. 1.2%).
Comment: This study demonstrates that the two ultrasound strategies are equivalent for diagnosing lower-extremity DVT. Two-point ultrasound is simple, convenient, and widely available, but this strategy requires repeat testing within 1 week in patients with normal ultrasound findings and elevated D-dimer results (30% of patients in this study). Whole-leg color-coded ultrasound provides a definitive result but might lead to unnecessary anticoagulation of small calf DVT that might otherwise resolve spontaneously.
Published in Journal Watch Emergency Medicine October 30, 2008
Bernardi E et al. Serial 2-point ultrasonography plus D-dimer vs whole-leg color-coded Doppler ultrasonography for diagnosing suspected symptomatic deep vein thrombosis: A randomized controlled trial. JAMA 2008 Oct 8; 300:1653.