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Bedside Tests vs. V/Q Scan for Ruling Out Pulmonary Embolism

A strategy using negative results on two of three bedside tests is as effective as V/Q scan.

Ventilation-perfusion (V/Q) scans are still commonly used for diagnosis of pulmonary embolism, even though they are expensive, cumbersome, and not uniformly available around the clock. These authors questioned whether any individual bedside tests or combination of tests performs as well as the V/Q scan for ruling out PE. They randomized 399 patients with suspected PE to undergo V/Q scan or three bedside tests: the Wells 7-item clinical score, D-dimer assay (latex agglutination), and alveolar dead-space fraction.

During a 3-month follow-up, a thromboembolic event occurred in 2.4% of patients in the bedside testing group (all of whom had negative results on at least 2 tests) and in 3.0% of patients in the V/Q scan group. Adding the alveolar dead-space fraction to the Wells score and D-dimer assay increased the number of patients in whom PE was excluded from 16% to 32%. The authors note that the alveolar dead-space fraction could not be determined in one third of patients.

Comment: These results, if validated, suggest that bedside evaluation of clinical and serologic factors may be as accurate as V/Q scanning in the diagnosis of PE. The type of D-dimer assay is key, though, because sensitivity varies widely. Alveolar dead-space testing improves diagnostic accuracy, but this test is not particularly useful because it is difficult to perform and requires arterial blood gas sampling. Now that the entire workup of pulmonary embolism occurs in the ED, additional strategies to eliminate certain tests or reduce costs are welcome.

— J. Stephen Bohan, MS, MD, FACP, FACEP

Published in Journal Watch Emergency Medicine March 28, 2006

Citation(s):

Rodger MA et al. The bedside investigation of pulmonary embolism diagnosis study: A double-blind randomized controlled trial comparing combinations of 3 bedside tests vs ventilation-perfusion scan for the initial investigation of suspected pulmonary embolism. Arch Intern Med 2006 Jan 23; 166:181-7.

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• Medline abstract (Free)

Moores LK. Diagnosis and management of pulmonary embolism: Are we moving toward an outcome standard? Arch Intern Med 2006 Jan 23; 166:147-8.

• Original article (Subscription may be required)
• Medline abstract (Free)