title: D-dimer in patients with clinically suspected pulmonary embolism.
abstract: OBJECTIVE
  To determine whether measurement of D-dimer, using an enzyme-linked immunosorbent assay (ELISA) with a cutoff of 300 ng/ml, and a latex agglutination assay with a cutoff of 500 ng/ml, is clinically useful in patients with suspected pulmonary embolism (PE).
  
  
  METHODS
  Prospective cohort.
  
  
  METHODS
  Tertiary care referral center, university-affiliated hospital.
  
  
  METHODS
  Two hundred twenty-one consecutive patients with clinically suspected PE.
  
  
  METHODS
  All patients had blood drawn to measure levels of D-dimer and underwent ventilation/perfusion (V/Q) lung scanning and bilateral impedance plethysmography (IPG); pulmonary angiography was performed in nine patients. Patients were classified as follows: (1) PE-positive; positive pulmonary angiography or high probability V/Q scan or non-high-probability V/Q scan and either abnormal IPG (either at presentation or on serial testing and confirmed by contrast venography) or symptomatic thromboembolic event within 3 months of presentation; or (2) PE-negative; normal V/Q scan or normal pulmonary angiography or non-high-probability V/Q scan and either normal serial IPG or abnormal IPG with normal venography and absence of symptomatic venous thromboembolism within 3 months of followup. Forty-three patients were classified as PE positive and 178 patients were classified as PE negative.
  
  
  RESULTS
  The sensitivities, specificities, positive predictive values, and negative predictive values of the ELISA and latex agglutination assay were calculated for all patients and for the subgroup of patients with non-high-probability V/Q scans. The ELISA D-dimer, using a cutoff of 300 ng/ml, showed a sensitivity and negative predictive value of 100 percent in all patients and patients with non-high-probability V/Q scans, but the corresponding specificities were only 26 percent and 13 percent, respectively. The latex agglutination assay for D-dimer using a cutoff of 500 ng/ml showed the following: sensitivities of 84 percent in all patients and 90 percent in patients with non-high-probability scans, negative predictive values of 93 percent in all patients, and 98 percent in patients with non-high-probability scans and specificities of 56 percent in all patients and 55 percent in patients with non-high-probability scans.
  
  
  CONCLUSIONS
  This study demonstrates that an ELISA D-dimer result of less than 300 ng/ml excludes PE but occurs in a small proportion of patients with clinically suspected PE. The latex agglutination assay, using a cutoff of 500 ng/ml, has potential clinical utility in excluding PE in the subgroup of patients with clinically suspected PE and non-high-probability V/Q scans. However, the 95 percent confidence interval on the observed sensitivity of the latex agglutination assay in patients with non-high-probability V/Q scans is wide. Therefore, these promising results should be confirmed in a large clinical trial before the latex agglutination assay is used to make management decisions.
authors.affiliation: Department of Medicine, McMaster University, Hamilton, Canada.
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: P A
authors.initials: PA
authors.lastname: Brill-Edwards
authors.forename: C
authors.initials: C
authors.lastname: Demers
authors.forename: D
authors.initials: D
authors.lastname: Donovan
authors.forename: A
authors.initials: A
authors.lastname: Panju
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D007841:Latex Fixation Tests; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D