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April 10, 1995

Impedance Plethysmography for Suspected Deep-Vein Thrombosis-Reply

Author Affiliations

Hamilton, Ontario

Ottawa, Ontario

Arch Intern Med. 1995;155(7):776. doi:10.1001/archinte.1995.00430070135018

In reply  We agree with Raskob and associates that the use of serial impedance plethysmography (IPG) is generally a safe approach in patients with suspected venous thromboembolism. Our recommendation that patients with a high pretest probability of deep-vein thrombosis (DVT) and a normal IPG undergo further testing is based on several considerations. First, Raskob and associates fail to cite one study1 in which the use of serial IPG in 381 consecutive patients with suspected DVT was associated with an unacceptably high rate of venous thromboembolism (10 patients [3.2%]), including four episodes of fatal pulmonary embolism, in follow-up. Although a novel IPG machine was used, its sensitivity for proximal DVT in a preliminary study was 91%, a rate consistent with those reported earlier.2 Fatal pulmonary embolism has also been reported in high-risk patients on the day of normal IPG testing.3 Second, our study showed that the sensitivity of