Use of a clinical model for safe management of patients with suspected pulmonary embolism

Ann Intern Med. 1998 Dec 15;129(12):997-1005. doi: 10.7326/0003-4819-129-12-199812150-00002.


Background: The low specificity of ventilation-perfusion lung scanning complicates the management of patients with suspected pulmonary embolism.

Objective: To determine the safety of a clinical model for patients with suspected pulmonary embolism.

Design: Prospective cohort study.

Setting: Five tertiary care hospitals.

Patients: 1239 inpatients and outpatients with suspected pulmonary embolism.

Interventions: A clinical model categorized pretest probability of pulmonary embolism as low, moderate, or high, and ventilation-perfusion scanning and bilateral deep venous ultrasonography were done. Testing by serial ultrasonography, venography, or angiography depended on pretest probability and lung scans.

Measurements: Patients were considered positive for pulmonary embolism if they had an abnormal pulmonary angiogram, abnormal ultrasonogram or venogram, high-probability ventilation-perfusion scan plus moderate or high pretest probability, or venous thromboembolic event during the 3-month follow-up. All other patients were considered negative for pulmonary embolism. Rates of pulmonary embolism during follow-up in patients who had a normal lung scan and those with a non-high-probability scan and normal serial ultrasonogram were compared.

Results: Pretest probability was low in 734 patients (3.4% with pulmonary embolism), moderate in 403 (27.8% with pulmonary embolism), and high in 102 (78.4% with pulmonary embolism). Three of the 665 patients (0.5% [95% CI, 0.1% to 1.3%]) with low or moderate pretest probability and a non-high-probability scan who were considered negative for pulmonary embolism had pulmonary embolism or deep venous thrombosis during 90-day follow-up; this rate did not differ from that in patients with a normal scan (0.6% [CI, 0.1% to 1.8%]; P > 0.2).

Conclusion: Management of patients with suspected pulmonary embolism on the basis of pretest probability and results of ventilation-perfusion scanning is safe.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Angiography
  • Decision Support Techniques*
  • Humans
  • Lung / diagnostic imaging
  • Lung / physiopathology
  • Probability
  • Prospective Studies
  • Pulmonary Embolism / diagnosis*
  • Pulmonary Embolism / physiopathology
  • Radionuclide Imaging
  • Reproducibility of Results
  • Risk Factors
  • Ultrasonography
  • Ventilation-Perfusion Ratio