title: Performance of helical computed tomography in unselected outpatients with suspected pulmonary embolism.
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.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  Emergency department of a teaching and community hospital.
  
  
  METHODS
  299 patients with clinically suspected pulmonary embolism and a plasma D -dimer level greater than 500 microgram/L.
  
  
  METHODS
  Pulmonary embolism was established by using a validated algorithm that included clinical assessment, lower-limb compression ultrasonography, lung scanning, and pulmonary angiography.
  
  
  METHODS
  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 (kappa = 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%.
  
  
  CONCLUSIONS
  Helical CT should not be used alone for suspected pulmonary embolism but could replace angiography in combined strategies that include ultrasonography and lung scanning.
authors.affiliation: Medical Clinic 1, Department of Internal Medicine, Geneva University Hospital, Rue Micheli-du-Crest 24, CH-1211 Geneva 14, Switzerland. Arnaud.Perrier@medecine.unige.ch
authors.forename: A
authors.initials: A
authors.lastname: Perrier
authors.forename: N
authors.initials: N
authors.lastname: Howarth
authors.forename: D
authors.initials: D
authors.lastname: Didier
authors.forename: P
authors.initials: P
authors.lastname: Loubeyre
authors.forename: P F
authors.initials: PF
authors.lastname: Unger
authors.forename: P
authors.initials: P
authors.lastname: de Moerloose
authors.forename: D
authors.initials: D
authors.lastname: Slosman
authors.forename: A
authors.initials: A
authors.lastname: Junod
authors.forename: H
authors.initials: H
authors.lastname: Bounameaux
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002170:Canada; D003663:Decision Trees; D004636:Emergency Service, Hospital; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D