Pulmonary Embolism: One Third of ED Imaging Avoidable

James Brice

June 05, 2012

June 5, 2012 — Up to one third of computed tomography (CT) and nuclear imaging scans for suspected pulmonary embolism are potentially avoidable if emergency department (ED) personnel were less aggressive in ordering the tests for low-risk patients, according to a new multicenter study involving 3849 patients at 11 US EDs. The study was published online June 4 in the Archives of Internal Medicine.

Arjun K. Venkatesh, MD, and colleagues in the Department of Emergency Medicine at Brigham and Womens/Massachusetts General Hospital, Boston, Massachusetts, determined that pulmonary CT and ventilation/qualification perfusion studies are potentially avoidable for many hemodynamically stable patients who are shown from their initial presentation to carry a low risk for PE.

The findings add credence to an efficiency measure for avoiding unnecessary medical imaging for PE diagnosis, endorsed by the National Quality Forum (NQF), a public–private partnership that advises the federal Agency for Healthcare Research and Quality on healthcare quality and measurement and reporting issues.

Dr. Venkatesh and colleagues note that the forum's initial recommendation was based on retrospective data suggesting that 7% to 25% of imaging studies can be avoided. This study adds more statistically powerful prospective data to guide imaging ordering behavior in the ED, he wrote.

The study focused on ED imaging behavior for the 2238 ED patients in the study who were recommended imaging to rule out the presence of PE, despite a low pretest probability of PE. These patients were hemodynamically stable (systolic blood pressure ≥90 mm Hg) and had Wells scores for pretest probability of less than 2 points. Other factors include the attending physician's opinion about the most likely diagnosis and their gestalt pretest probability.

Findings demonstrated the value of D-dimer testing. About 11% of the avoidable imaging studies were derived from 394 patients who underwent imaging despite negative D-dimer results.

The remaining 22% of avoidable imaging studies were associated with the potential application of the NQF criteria for 1427 patients who did not undergo D-dimer testing.

Fifty patients (1.3% of those imaged) were diagnosed with PE by imaging considered potentially avoidable by the NQF measure because no D-dimer testing was performed. The researchers identified only 8 cases (0.2%) of patients who had a negative D-dimer before a positive diagnosis for PE with imaging considered avoidable.

Assuming 100% imaging specificity, Dr. Venkatesh and colleagues estimated that adherence to the NQF guideline would have led to 11 missed pulmonary emboli from 8 patients with negative D-dimer test results and 3 patients who had not undergone D-dimer testing (93% sensitivity).

Multivariate analysis demonstrated the likelihood that imaging can be avoided decreased with increasing patient age or the presence of an inactive cancer, sickle cell disease, and pregnancy.

"Our results demonstrate the validity of the NQF measure and refute the notion that high measure performance is associated with the unintended consequence of missed PE," the authors write.

They stress that they study was limited to identifying potentially avoidable studies, not definitely avoidable imaging workups for patients with no D-dimer testing performed. More research would be needed to make that determination.

The study was supported by the National Institutes of Health. Dr. Venkatesh was part of the writing group that authored the NQF quality measure related to pulmonary embolism imaging. The other authors have disclosed no relevant financial relationships.

Arch Intern Med. Published online June 4, 2012. Full text

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