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D-dimer Testing Reduces Need for Ultrasound in Diagnosis of DVT

Patients with a low clinical probability of DVT and a negative D-dimer test can forego further testing.

The use of D-dimer testing to diagnose deep venous thrombosis (DVT) has been assessed previously, but none of the studies was randomized and controlled. In this randomized, controlled study, the authors used a pretest clinical scoring system to categorize patients as either likely or unlikely to have DVT. Patients were then randomized to undergo ultrasound imaging alone or D-dimer testing (using either the SimpliRed assay or IL-Test) followed by ultrasound imaging if the D-dimer test was positive or if the patient was judged likely to have DVT; if the D-dimer test was negative and the patient was categorized as unlikely to have DVT, the diagnosis was considered ruled out, and no further testing was done. In the control group, ultrasound was repeated after 1 week if the initial result was negative. The study endpoint was development of DVT or pulmonary embolism at 90 days.

A total of 1096 patients were randomized. The prevalence of DVT was 16% overall -- 28% in the 495 patients who had been scored as likely to have DVT and 5% in the 601 patients judged unlikely to have DVT. Among 218 patients who were judged unlikely to have DVT and who had negative D-dimer tests, only 0.9% had confirmed thrombosis during follow-up.

Comment: This study is a major contribution to clinical decision making and patient safety. A low clinical probability for DVT combined with a negative D-dimer test means "STOP" -- the patient does not require further testing. If this decision guide is to be followed, clinicians must use the reasonably simple scoring system used by these authors (detailed in the original article). Use of this strategy should significantly reduce the need for venous ultrasound without any decrement in diagnostic accuracy or patient safety.

— J. Stephen Bohan, MS, MD, FACP, FACEP

Published in Journal Watch Emergency Medicine October 29, 2003

Citation(s):

Wells PS et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med 2003 Sep 25; 349:1227-35.

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• Medline abstract (Free)