title: An evaluation of D-dimer in the diagnosis of pulmonary embolism: a randomized trial.
abstract: BACKGROUND
  It may be safe to omit additional diagnostic testing in selected patients with suspected pulmonary embolism (PE) who have a negative D-dimer test, but this approach has never been evaluated in a randomized, controlled trial.
  
  
  OBJECTIVE
  To determine if additional diagnostic testing can be safely withheld in patients with suspected PE who have negative erythrocyte agglutination D-dimer test results.
  
  
  METHODS
  Randomized comparisons in 2 subgroups of a prospective multicenter study.
  
  
  METHODS
  7 university hospitals.
  
  
  METHODS
  1126 outpatients or inpatients with suspected PE; of these, 456 patients with negative erythrocyte agglutination D-dimer test results were randomly assigned to the intervention groups. Patients were classified into 2 clinical probability groups: those with a low clinical probability of PE (low-probability group) and those with a moderate or high clinical probability of PE, a nondiagnostic ventilation-perfusion lung scan, and no evidence of proximal deep venous thrombosis on bilateral ultrasonography (moderate- or high-probability group).
  
  
  METHODS
  The experimental intervention for both probability groups was no further diagnostic testing for PE. The control intervention for the low-probability group was a ventilation-perfusion lung scan followed by ultrasonography of the proximal deep veins of the legs on the same day. If the lung scan was nondiagnostic, ultrasonography of the legs was repeated 7 and 14 days later. The control intervention for the moderate- or high-probability group was ultrasonography of the proximal deep veins of the legs after 7 and 14 days. In the control and experimental groups, anticoagulation was withheld or withdrawn if PE was not diagnosed.
  
  
  METHODS
  Symptomatic venous thromboembolism (VTE) during 6 months of follow-up.
  
  
  RESULTS
  Prevalence of VTE was 15.2% in the 1126 enrolled patients. In the low-probability group, VTE occurred during follow-up in 0 of 182 patients who had no additional diagnostic testing and in 1 of 185 patients who had additional testing (difference, -0.5 percentage point [95% CI, -3.0 to 1.6 percentage points]). In the moderate- or high-probability group, VTE occurred during follow-up in 1 of 41 patients who had no additional diagnostic testing and in 0 of 41 patients who had additional testing (difference, 2.4 percentage points [CI, -6.4 to 12.6 percentage points]).
  
  
  CONCLUSIONS
  The authors could not enroll 2000 patients as originally planned; 3 randomly assigned patients did not receive the allocated intervention, and 7 received inadequate follow-up. Personnel who performed follow-up evaluations were not blinded to the results of diagnostic testing at enrollment or to allocation group assignments.
  
  
  CONCLUSIONS
  In patients with a low probability of PE who have negative D-dimer results, additional diagnostic testing can be withheld without increasing the frequency of VTE during follow-up. Low clinical probability and negative D-dimer results occur in 50% of outpatients and in 20% of inpatients with suspected PE.
authors.affiliation: McMaster University and the Henderson Research Centre, Hamilton, Ontario, Canada. kearonc@mcmaster.ca
authors.forename: Clive
authors.initials: C
authors.lastname: Kearon
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: James
authors.initials: J
authors.lastname: Douketis
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Turpie
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Bates
authors.forename: Agnes Y
authors.initials: AY
authors.lastname: Lee
authors.forename: Mark A
authors.initials: MA
authors.lastname: Crowther
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Weitz
authors.forename: Patrick
authors.initials: P
authors.lastname: Brill-Edwards
authors.forename: Philip
authors.initials: P
authors.lastname: Wells
authors.forename: David R
authors.initials: DR
authors.lastname: Anderson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: Lori-Ann
authors.initials: LA
authors.lastname: Linkins
authors.forename: Jim A
authors.initials: JA
authors.lastname: Julian
authors.forename: Laura R
authors.initials: LR
authors.lastname: Bonilla
authors.forename: Michael
authors.initials: M
authors.lastname: Gent
mesh_terms: D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D005500:Follow-Up Studies; D006801:Humans; D007297:Inpatients; D017063:Outcome Assessment, Health Care; D010045:Outpatients; D011336:Probability; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D020246:Venous Thrombosis / Q000175:diagnosis*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D