Blood Clots: Single Ultrasound may be Enough
(Ivanhoe Newswire) -- Multiple ultrasounds may not be necessary for some patients with a suspected blood clot in a deep vein of a leg, and withholding anticoagulation therapy after a negative whole-leg ultrasound is associated with a low risk of developing a blood clot during the subsequent three months.
Compression ultrasound (CUS) is the customary testing procedure used to diagnose deep vein thrombosis (DVT), a blood clot in a deep vein in the thigh or leg. The CUS method confirms and excludes DVT in the veins above the knee (proximal veins), but its accuracy for veins below the knee (distal veins) has been questioned. Up to 25 percent of distal DVTs may migrate upward into proximal veins, increasing the risk of pulmonary embolism, or a blood clot in the veins moving into the lung.
Stacy A. Johnson, M.D., of the University of Utah School of Medicine in Salt Lake City, and colleagues conducted a meta-analysis to examine the risk of blood clots in the deep veins of the legs or in the lungs (venous thromboembolism) in patients with suspected lower-extremity DVT following a single negative whole-leg CUS and withholding anticoagulation. The authors identified seven studies, which included 4,731 patients.
Whole-leg CUS may exclude proximal and distal DVT in a single evaluation and lessen the need for repeat CUS tests. However, concerns exist regarding the safety of using a single whole-leg CUS to exclude DVT following an initially negative result.
"Consequently, practice guidelines recommend serial CUS of the proximal veins 5 to 7 days after an initial negative result to safely exclude clinically suspected DVT," study authors wrote. "Because only 1 percent to 2 percent of repeat CUS tests detect thrombus propagation, many repeat studies are conducted to detect a small number of DVTs."
The data indicated venous thromboembolism or suspected venous thromboembolism-related death occurred in 34 patients, including 11 with distal DVT, seven with proximal DVT, seven with non-fatal pulmonary emboli, and nine who died, possibly from venous thromboembolism.
"In summary, withholding anticoagulation following a single negative whole-leg CUS result was associated with a low risk for venous thromboembolism during 3-month follow-up in patients with suspected DVT," authors concluded. "Using a single negative whole-leg CUS result as the sole diagnostic modality in patients with high pretest probability of DVT requires further study."
SOURCE: Journal of the American Medical Association (JAMA), February 3, 2010
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