Impact of a rapid rule-out protocol for pulmonary embolism on the rate of screening, missed cases, and pulmonary vascular imaging in an urban US emergency department

Ann Emerg Med. 2004 Nov;44(5):490-502. doi: 10.1016/j.annemergmed.2004.03.018.


Study objective: This study tests the hypothesis that implementation of a point-of-care emergency department (ED) protocol to rule out pulmonary embolism would increase the rate of evaluation without increasing the rate of pulmonary vascular imaging or ED length of stay and that less than 1.0% of patients with a negative protocol would have an adverse outcome.

Methods: A baseline study was conducted on patients with suspected pulmonary embolism at an urban ED to establish baseline measurements performed when only pulmonary vascular imaging was available to rule out pulmonary embolism. The intervention protocol used pretest probability assessment, a whole-blood d -dimer assay, and an alveolar dead-space measurement to rule out pulmonary embolism. The main outcomes were diagnosis of venous thromboembolism or sudden unexpected death within 90 days.

Results: During baseline, 453 of 61,322 patients (0.74%; 95% confidence interval [CI] 0.67% to 0.81%) underwent pulmonary vascular imaging, and 8% (95% CI 6% to 11%) of scan results were positive; 1.20% (95% CI 0.39% to 2.78%) of untreated discharged patients were anticoagulated for venous thromboembolism or died unexpectedly within 90 days. The median length of stay was 385 minutes. After intervention, 1,460 of 102,848 patients (1.42%; 95% CI 1.35% to 1.49%) were evaluated for pulmonary embolism. Seven hundred fifty-two patients had a negative protocol and 5 of 752 (0.66%; 95% CI 0.20% to 1.54%) had venous thromboembolism within 90 days, none with unexpected death. After intervention, the rate of pulmonary vascular imaging tended to decrease (0.64%; 95% CI 0.59% to 0.69%), and more scans (11%; 95% CI 9% to 14%) were read as positive; the length of stay decreased to 297 minutes.

Conclusion: A point-of-care pulmonary embolism rule-out protocol doubled the rate of screening for pulmonary embolism in the ED, had a false negative rate of less than 1.0%, did not increase the pulmonary vascular imaging rate, and decreased length of stay.

MeSH terms

  • Adult
  • Algorithms
  • Angiography / methods
  • Clinical Protocols
  • Death, Sudden / epidemiology
  • Decision Support Techniques
  • Emergency Service, Hospital
  • Feasibility Studies
  • Female
  • Fibrin Fibrinogen Degradation Products / analysis
  • Hospitals, Urban
  • Humans
  • Length of Stay
  • Likelihood Functions
  • Lung / blood supply
  • Male
  • Middle Aged
  • North Carolina / epidemiology
  • Predictive Value of Tests
  • Pulmonary Embolism / diagnosis*
  • Pulmonary Embolism / epidemiology
  • Respiratory Dead Space
  • Tomography, X-Ray Computed
  • Venous Thrombosis / epidemiology
  • Ventilation-Perfusion Ratio


  • Fibrin Fibrinogen Degradation Products
  • fibrin fragment D