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Pair of Bedside Tests Excludes Pulmonary Embolism

Authors of a 1997 study suggested that the diagnosis of pulmonary embolism could be excluded by a combination of 2 tests: D-dimer assay and alveolar dead-space fraction (ADSF). The rationale was that an abnormal D-dimer assay suggests the presence of intravascular thrombus and an elevated ADSF indicates the presence of pulmonary vascular obstruction. In a multicenter, prospective, noninterventional trial led by the same principal investigator, a convenience cohort of 380 hemodynamically stable, adult ED patients with suspected pulmonary embolism (PE) underwent these 2 tests before ventilation-perfusion scanning or helical chest computed tomography. The trial was supported in part by the manufacturers of the devices and assays investigated.

Both volumetric capnography to calculate ADSF and D-dimer testing using a heparinized arterial whole blood agglutination assay were performed at bedside. PE was diagnosed based on standard radiologic criteria in 64 patients (16.8 percent); of these, 20 had an abnormal D-dimer assay only, 3 had an abnormal ADSF only, 40 had abnormal results on both, and 1 (the sole false-negative) had normal results on both. An abnormal result on either or both tests had a sensitivity for PE of 98.4 percent and a specificity of 51.6 percent.

Comment: Current methods of diagnosing PE are invasive, cumbersome, prolonged, and extraordinarily resource-consumptive. A simple screening tool has been high on the wish list of EPs, given the myriad clinical presentations of this life-threatening diagnosis. These findings suggest that a negative whole blood agglutination D-dimer assay coupled with a normal alveolar dead-space fraction is associated with a probability of PE of less than 1 percent in stable patients deemed at risk for the condition.

— JA Marx

Published in Journal Watch Emergency Medicine May 2, 2001

Citation(s):

Kline JA et al. Diagnostic accuracy of a bedside D-dimer assay and alveolar dead-space measurement for rapid exclusion of pulmonary embolism: A multicenter study. JAMA 2001 Feb 14 285 761-768.

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