title: Combination pretest probability assessment and D-dimer did not reduce outpatient imaging for venous thromboembolism in a tertiary care hospital emergency department.
abstract: BACKGROUND
  Venous thromboembolism (VTE) is difficult to diagnose yet potentially life threatening. A low-risk pretest probability (PTP) assessment combined with a negative D-dimer can rule out VTE in two-thirds of outpatients, reducing the need for imaging. Real-life implementation of this strategy is associated with several challenges.
  
  
  METHODS
  We evaluated the impact of introducing a standardized diagnostic algorithm including a mandatory PTP assessment and D-dimer on radiologic test use for VTE in our emergency department (ED). A retrospective review of all ED visits for suspected VTE in the year prior to and following the introduction of this algorithm was conducted. VTE diagnosis was based on imaging. Guideline compliance was also assessed.
  
  
  RESULTS
  ED visits were investigated for suspected VTE in the pre- and postintervention periods (n  =  1,785). Most D-dimers (95%) ordered were associated with a PTP assessment, and 50% of visits assigned a low PTP had a negative D-dimer. The proportion of imaging tests ordered for VTE in all ED visits was unchanged postintervention (1.9% v. 2.0%). The proportion of patients with suspected VTE in whom VTE was confirmed on imaging decreased postintervention (10.2% v. 14.1%).
  
  
  CONCLUSIONS
  In spite of excellent compliance with our algorithm, we were unable to reduce imaging for VTE. This may be due to a lower threshold for suspecting VTE and an increase in investigation for VTE combined with a high false positive rate of our D-dimer assay in low-pretest probability patients. This study highlights two common real-life challenges with adopting this strategy for VTE investigation.
authors.forename: Sarah
authors.initials: S
authors.lastname: Ingber
authors.forename: Rita
authors.initials: R
authors.lastname: Selby
authors.forename: Jacques
authors.initials: J
authors.lastname: Lee
authors.forename: William
authors.initials: W
authors.lastname: Geerts
authors.forename: Elena
authors.initials: E
authors.lastname: Brnjac
mesh_terms: D000465:Algorithms; D003952:Diagnostic Imaging / Q000706:statistics & numerical data*; D004636:Emergency Service, Hospital; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D011336:Probability; D011655:Pulmonary Embolism / Q000175:diagnosis / Q000453:epidemiology; D018570:Risk Assessment; D012307:Risk Factors; D062606:Tertiary Care Centers; D054556:Venous Thromboembolism / Q000175:diagnosis* / Q000453:epidemiology*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D