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New Way to Rule Out Pulmonary Embolism?

Patients in whom pulmonary embolism (PE) is suspected would benefit from improved diagnostic strategies. A rapid, minimally invasive approach with nearly perfect sensitivity and acceptable specificity would reduce unnecessary tests and treatments. In this prospective, multicenter study, supported partially by the manufacturers of the investigated products, researchers sought to determine whether combining D-dimer assay with alveolar dead-space measurement could effectively rule out PE.

The researchers enrolled 380 emergency department (ED) patients (selected from a total of 1384) who presented with suspected PE. They measured D-dimer (using a whole-blood agglutination assay) and alveolar dead space (derived from arterial pCO₂ plus a 2-minute bedside measurement of expired CO₂), and attempted to establish the diagnosis of PE by record review and telephone follow-up. Of the 64 patients diagnosed with PE, only 1 had both a negative D-dimer and normal alveolar dead-space fraction; sensitivity was therefore 98.4 percent if the investigators' diagnosis of PE was correct. The specificity was 51.6 percent.

Comment: The combination of whole-blood D-dimer and alveolar dead-space measurement appeared highly sensitive for the detection of pulmonary embolism in this study, but because pulmonary angiograms were not done in all patients, the number of patients identified as having PE may have been falsely low, and the sensitivity of the test may therefore have been overestimated. Because failure to diagnose PE can have grave consequences, application of this method should await more convincing demonstration of its accuracy. -- WC Taylor, Associate Editor, and Charles A. Morris, MD, Brigham and Women's Hospital, Boston

Published in Journal Watch General Medicine March 9, 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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