title: Inappropriate use and interpretation of D-dimer testing in the emergency department: an unexpected adverse effect of meeting the "4-h target".
abstract: BACKGROUND
  D-dimer tests were inappropriately overused in our emergency department as a result of bloods being taken before clinical assessment to help meet the "4-hour target". We introduced a multifaceted intervention to reduce the number of inappropriate D-dimer tests. The secondary aim was to improve the diagnostic workup of suspected pulmonary embolism (PE).
  
  
  METHODS
  Rate of D-dimer test and ventilation/perfusion scan requests were compared before, during and after a staggered intervention at two hospitals in one National Health Service Trust. Audits before and after the intervention were done to determine whether test use was appropriate and whether the diagnostic workup was complete.
  
  
  RESULTS
  At hospital 1, D-dimer testing after the intervention was almost halved: ratio 0.59 (95% CI 0.55 to 0.63) (p<0.0001). There was also a small reduction at hospital 2 (control): rate 0.88 (95% CI 0.78 to 0.99) (p = 0.03). After the formal introduction of change at hospital 2, there was a further reduction in tests: ratio 0.67 (95% CI 0.58 to 0.76) (p<0.0001). In hospital 1, pretest probability assessment improved by 42% (p = 0.0004) and D-dimer test use was reduced by 12.5% (p = 0.04) between audits. Improvement in the use of D-dimer test according to the pathway was not significant (32.5%, p = 0.11), and there was no change in the proportion of patients with completion of their diagnostic workup for PE: 47.6% (95% CI 38.3% to 56%) before and 45.6% (95% CI 38.3% to 53.1%) after the intervention.
  
  
  CONCLUSIONS
  Implementation of a multifaceted change program reduced the number of D-dimer test requests in both hospitals and may have improved the diagnostic workup for PE at hospital 1. Processes that speed patient transit through the emergency department may impact negatively on other aspects of patient care. This should be the subject of further studies.
authors.affiliation: Department of Emergency Medicine, Auckland City Hospital, Private Bag 92024, Auckland Mail Centre, Auckland 1142, New Zealand. peterj@adhb.govt.nz
authors.forename: P
authors.initials: P
authors.lastname: Jones
authors.forename: B
authors.initials: B
authors.lastname: Elangbam
authors.forename: N R
authors.initials: NR
authors.lastname: Williams
mesh_terms: D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis / Q000706:statistics & numerical data; D054869:Clinical Audit; D004636:Emergency Service, Hospital; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006300:Health Services Misuse; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D