title: Computed tomographic pulmonary angiography vs ventilation-perfusion lung scanning in patients with suspected pulmonary embolism: a randomized controlled trial.
abstract: BACKGROUND
  Ventilation-perfusion (V(dot)Q(dot) lung scanning and computed tomographic pulmonary angiography (CTPA) are widely used imaging procedures for the evaluation of patients with suspected pulmonary embolism. Ventilation-perfusion scanning has been largely replaced by CTPA in many centers despite limited comparative formal evaluations and concerns about CTPA's low sensitivity (ie, chance of missing clinically important pulmonary embuli).
  
  
  OBJECTIVE
  To determine whether CTPA may be relied upon as a safe alternative to V(dot)Q(dot scanning as the initial pulmonary imaging procedure for excluding the diagnosis of pulmonary embolism in acutely symptomatic patients.
  
  
  METHODS
  Randomized, single-blinded noninferiority clinical trial performed at 4 Canadian and 1 US tertiary care centers between May 2001 and April 2005 and involving 1417 patients considered likely to have acute pulmonary embolism based on a Wells clinical model score of 4.5 or greater or a positive D-dimer assay result.
  
  
  METHODS
  Patients were randomized to undergo either V(dot)Q(dot scanning or CTPA. Patients in whom pulmonary embolism was considered excluded did not receive antithrombotic therapy and were followed up for a 3-month period.
  
  
  METHODS
  The primary outcome was the subsequent development of symptomatic pulmonary embolism or proximal deep vein thrombosis in patients in whom pulmonary embolism had initially been excluded.
  
  
  RESULTS
  Seven hundred one patients were randomized to CTPA and 716 to V(dot)Q(dot scanning. Of these, 133 patients (19.2%) in the CTPA group vs 101 (14.2%) in the V(dot)Q(dot scan group were diagnosed as having pulmonary embolism in the initial evaluation period (difference, 5.0%; 95% confidence interval [CI], 1.1% to 8.9%) and were treated with anticoagulant therapy. Of those in whom pulmonary embolism was considered excluded, 2 of 561 patients (0.4%) randomized to CTPA vs 6 of 611 patients (1.0%) undergoing V(dot)Q(dot scanning developed venous thromboembolism in follow-up (difference, -0.6%; 95% CI, -1.6% to 0.3%) including one patient with fatal pulmonary embolism in the V(dot)Q(dot group.
  
  
  CONCLUSIONS
  In this study, CTPA was not inferior to V(dot)Q(dot scanning in ruling out pulmonary embolism. However, significantly more patients were diagnosed with pulmonary embolism using the CTPA approach. Further research is required to determine whether all pulmonary emboli detected by CTPA should be managed with anticoagulant therapy.
  
  
  BACKGROUND
  isrctn.org Identifier: ISRCTN65486961.
authors.affiliation: Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada. david.anderson@dal.ca
authors.forename: David R
authors.initials: DR
authors.lastname: Anderson
authors.forename: Susan R
authors.initials: SR
authors.lastname: Kahn
authors.forename: Marc A
authors.initials: MA
authors.lastname: Rodger
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: Tim
authors.initials: T
authors.lastname: Morris
authors.forename: Andrew
authors.initials: A
authors.lastname: Hirsch
authors.forename: Eddy
authors.initials: E
authors.lastname: Lang
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.forename: George
authors.initials: G
authors.lastname: Kovacs
authors.forename: Jon
authors.initials: J
authors.lastname: Dreyer
authors.forename: Carol
authors.initials: C
authors.lastname: Dennie
authors.forename: Yannick
authors.initials: Y
authors.lastname: Cartier
authors.forename: David
authors.initials: D
authors.lastname: Barnes
authors.forename: Erica
authors.initials: E
authors.lastname: Burton
authors.forename: Susan
authors.initials: S
authors.lastname: Pleasance
authors.forename: Chris
authors.initials: C
authors.lastname: Skedgel
authors.forename: Keith
authors.initials: K
authors.lastname: O'Rouke
authors.forename: Philip S
authors.initials: PS
authors.lastname: Wells
mesh_terms: D000328:Adult; D000368:Aged; D000792:Angiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed; D014692:Ventilation-Perfusion Ratio