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Ruling Out DVT Without Ultrasound

A rapid D-dimer assay was used to rule out deep-vein thrombosis in outpatients with low clinical probability of DVT.

Although ultrasound is used to evaluate most patients with suspected deep-vein thrombosis (DVT), study results suggest that a combination of D-dimer testing and clinical probability assessment is an efficient and cost-effective alternative (Journal Watch Aug 14 2001 and Journal Watch Oct 14 2003). This systematic review corroborates those individual findings.

Investigators identified 12 studies (that involved 5000 outpatients), in which rapid D-dimer assays were performed and explicit clinical criteria were used to classify patients as having low, medium, or high pretest probability of lower-extremity DVT. In probability assessments, clinicians assigned points to risk factors and clinical findings (e.g., cancer, immobilization, leg swelling) and deducted points when an alternative diagnosis was deemed more likely. The presence of DVT was determined objectively (by ultrasound, venography, or plethysmography), and all studies included at least 3 months of follow-up.

When a less sensitive D-dimer assay (the SimpliRED assay) was used, the 3-month cumulative incidence of DVT was 0.5% among patients with negative assay results and low pretest probability. When a more sensitive assay was used, the incidence was 0.4% in patients with negative assay results and low or medium pretest probability of DVT.

Comment: In outpatients with low probability of deep-vein thrombosis based on clinical criteria, normal D-dimer assay results effectively rule out DVT. With a more sensitive assay, DVT can even be ruled out when the clinical probability is medium. In either of these situations, ultrasound probably is unnecessary. At the time of publication, the full text of the original article was available free of charge.

— Keith I. Marton, MD

Published in Journal Watch General Medicine November 5, 2004

Citation(s):

Fancher TL et al. Combined use of rapid D-dimer testing and estimation of clinical probability in the diagnosis of deep vein thrombosis: Systematic review. BMJ 2004 Oct 9; 329:821-4.

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