title: Sensitivity and specificity of a rapid whole-blood assay for D-dimer in the diagnosis of pulmonary embolism.
abstract: BACKGROUND
  Patients with suspected pulmonary embolism often have nondiagnostic lung scans and may present in circumstances where lung scanning is unavailable. Levels of D-dimer, a fibrin-specific product, are increased in patients with acute thrombosis; this may simplify the diagnosis of pulmonary embolism.
  
  
  OBJECTIVE
  To determine the sensitivity and specificity of a whole-blood D-dimer assay in patients with suspected pulmonary embolism and in subgroups of patients with low pretest probability of pulmonary embolism or nondiagnostic lung scans.
  
  
  METHODS
  Prospective cohort.
  
  
  METHODS
  Four tertiary care hospitals.
  
  
  METHODS
  1177 consecutive patients with suspected pulmonary embolism.
  
  
  METHODS
  All patients underwent an assessment of pretest probability by use of a standardized clinical model, a D-dimer assay, ventilation-perfusion lung scanning, and bilateral compression ultrasonography. Patients in whom pulmonary embolism was not initially diagnosed were followed for 3 months. Accordingly, patients were categorized as positive or negative for pulmonary embolism.
  
  
  RESULTS
  Of the 1177 patients, 197 (17%) were classified as positive for pulmonary embolism. Overall, the D-dimer assay showed a sensitivity of 84.8% and a specificity of 68.4%. In 703 patients (3.4%) with a low pretest probability of pulmonary embolism, the likelihood ratio associated with a negative D-dimer test result was 0.27, resulting in a posterior probability of 1.0% (95% CI, 0.3% to 2.2%). In 698 patients with nondiagnostic lung scans (previous probability, 7.4%), the likelihood ratio associated with a negative D-dimer test result was 0.36, resulting in a posterior probability of 2.8% (CI, 1.4% to 4.8%).
  
  
  CONCLUSIONS
  A normal D-dimer test result is useful in excluding pulmonary embolism in patients with a low pretest probability of pulmonary embolism or a nondiagnostic lung scan.
authors.affiliation: McMaster University, Hamilton, Ontario, Canada.
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: P S
authors.initials: PS
authors.lastname: Wells
authors.forename: C
authors.initials: C
authors.lastname: Kearon
authors.forename: D
authors.initials: D
authors.lastname: Anderson
authors.forename: M
authors.initials: M
authors.lastname: Crowther
authors.forename: J I
authors.initials: JI
authors.lastname: Weitz
authors.forename: J
authors.initials: J
authors.lastname: Bormanis
authors.forename: P
authors.initials: P
authors.lastname: Brill-Edwards
authors.forename: A G
authors.initials: AG
authors.lastname: Turpie
authors.forename: B
authors.initials: B
authors.lastname: MacKinnon
authors.forename: M
authors.initials: M
authors.lastname: Gent
authors.forename: J
authors.initials: J
authors.lastname: Hirsh
mesh_terms: D000465:Algorithms; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D016013:Likelihood Functions; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D014692:Ventilation-Perfusion Ratio
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D