Performance of Helical Computed Tomography in Unselected Outpatients with Suspected Pulmonary Embolism

  1. Arnaud Perrier, MD;
  2. Nigel Howarth, MD;
  3. Dominique Didier, MD;
  4. Pierre Loubeyre, MD;
  5. Pierre-François Unger, MD;
  6. Philippe de Moerloose, MD;
  7. Daniel Slosman, MD;
  8. Alain Junod, MD; and
  9. Henri Bounameaux, MD
  1. From Geneva University Hospital, Geneva, Switzerland.

    Abstract

    Background: Helical computed tomography (CT) is commonly used to diagnose pulmonary embolism, although its operating characteristics have been insufficiently evaluated.

    Objective: To assess the sensitivity and specificity of helical CT in suspected pulmonary embolism.

    Design: Observational study.

    Setting: Emergency department of a teaching and community hospital.

    Patients: 299 patients with clinically suspected pulmonary embolism and a plasma d-dimer level greater than 500 µg/L.

    Intervention: Pulmonary embolism was established by using a validated algorithm that included clinical assessment, lower-limb compression ultrasonography, lung scanning, and pulmonary angiography.

    Measurements: Sensitivity, specificity, and likelihood ratios of helical CT and interobserver agreement. Helical CT scans were withheld from clinicians and were read 3 months after acquisition by radiologists blinded to all clinical data.

    Results: 118 patients (39%) had pulmonary embolism. In 12 patients (4%), 2 of whom had pulmonary embolism, results of helical CT were inconclusive. For patients with conclusive results, sensitivity of helical CT was 70% (95% CI, 62% to 78%) and specificity was 91% (CI, 86% to 95%). Interobserver agreement was high (κ = 0.823 to 0.902). The false-negative rate was lower for helical CT used after initial negative results on ultrasonography than for helical CT alone (21% vs. 30%). Use of helical CT after normal results on initial ultrasonography and nondiagnostic results on lung scanning had a false-negative rate of only 5% and a false-positive rate of only 7%.

    Conclusion: Helical CT should not be used alone for suspected pulmonary embolism but could replace angiography in combined strategies that include ultrasonography and lung scanning.

    Article and Author Information

    • Acknowledgments: The authors thank A. Bigaroni, MD, and S. Bernard Bagattini, MD, for data management; Ph. Minazio and G. Reber, PhD, for laboratory assistance; and P. Bachmann for invaluable help in managing all technical aspects of helical computed tomography. They also thank all the residents of Medical Clinics 1 and 2 for their assistance in including and working up the patients in the study, and all the residents and technicians from the radiodiagnosis division who participated in the study.

    • Grant Support: By the Swiss National Research Foundation (32-52798.97) and by an unrestricted grant from Roche Pharma Switzerland.

    • Requests for Single Reprints: Arnaud Perrier, MD, Medical Clinic 1, Department of Internal Medicine, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland; e-mail, Arnaud.Perrier{at}medecine.unige.ch

    • Current Author Addresses: Drs. Perrier and Junod: Medical Clinic 1, Department of Internal Medicine, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland.

    • Drs. Howarth, Didier, and Loubeyre: Division of Radiodiagnosis, Department of Radiology, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland.

    • Dr. Unger: Division of Medical and Surgical Emergencies, Department of Internal Medicine, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland.

    • Drs. de Moerloose and Bounameaux: Division of Angiology and Hemostasis, Department of Internal Medicine, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland.

    • Dr. Slosman: Division of Nuclear Medicine, Department of Radiology, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland.

    • Author Contributions: Conception and design: A. Perrier, N. Howarth, P.-F. Unger, P. de Moerloose, D. Slosman, A. Junod, H. Bounameaux.

    • Analysis and interpretation of the data: A. Perrier, N. Howarth, D. Didier, P. Loubeyre, A. Junod, H. Bounameaux.

    • Drafting of the article: A. Perrier, H. Bounameaux.

    • Critical revision of the article for important intellectual content: A. Perrier, N. Howarth, P.-F. Unger, P. de Moerloose, D. Slosman, A. Junod, H. Bounameaux.

    • Final approval of the article: A. Perrier, N. Howarth, D. Didier, P. Loubeyre, P.-F. Unger, P. de Moerloose, D. Slosman, A. Junod, H. Bounameaux.

    • Provision of study materials or patients: A. Perrier, N. Howarth, D. Didier, P. Loubeyre, D. Slosman, H. Bounameaux.

    • Obtaining of funding: A. Perrier, N. Howarth, A. Junod, H. Bounameaux.

    • Administrative, technical, or logistic support: N. Howarth, P. Loubeyre, P.-F. Unger, P. de Moerloose, D. Slosman, H. Bounameaux.

    • Collection and assembly of data: A. Perrier, N. Howarth, P. Loubeyre, H. Bounameaux.

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    1. Ann Intern Med July 17, 2001 vol. 135 no. 2 88-97
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