title: Effect of two different FDA-approved D-dimer assays on resource utilization in the emergency department.
abstract: BACKGROUND
  The D-dimer assay has been shown to be an appropriate test to rule out pulmonary embolism (PE) in low-risk patients in the emergency department (ED). Multiple assays now are approved to measure D-dimer levels. Studies have shown a newer assay, Tina-quant, to have similar diagnostic accuracy to the VIDAS assay.
  
  
  OBJECTIVE
  The objective was to determine effects of transitioning from the VIDAS assay to the Tina-quant D-dimer assay on the need for computed tomography angiogram (CTA) and ED length of stay (LOS) in patients being evaluated for PE in the ED.
  
  
  METHODS
  A retrospective cohort study was conducted of patients who had D-dimer levels ordered at an urban, academic, Level I trauma center with over 55,000 annual ED visits. The results of D-dimer levels in the ED were recorded over a period of 6 months prior to and 6 months after the transition to the new D-dimer assay. The numbers of positive and negative D-dimers and need for subsequent CTAs were recorded for comparison. LOS was also recorded to determine time saved. Medians were calculated and compared using Wilcoxon rank sum.
  
  
  RESULTS
  During the initial period, 875 D-dimers were ordered, with a positive rate of 41.5%. During the period after the introduction of the Tina-quant assay, 859 tests were ordered, with 25.5% having positive results. An absolute decrease of 16% in the number of necessary CTAs (p < 0.003) was seen after the transition to the Tina-quant assay. LOS data showed a mean LOS of 481 minutes in the ED for patients who underwent testing with the Tina-quant assay compared to 526 minutes with the VIDAS assay, saving an average of 45 minutes per patient (p < 0.003). The positive rate on performed imaging studies for D-dimer of > 500 rose from 13 of 308 (4.2%) to 17 of 187 (9.1%).
  
  
  CONCLUSIONS
  Switching D-dimer assays reduced both LOS and number of imaging studies in our patient population.
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA. leon_sanchez@bidmc.harvard.edu
authors.forename: Leon D
authors.initials: LD
authors.lastname: Sanchez
authors.forename: Daniel C
authors.initials: DC
authors.lastname: McGillicuddy
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Volz
authors.forename: Shu-Ling
authors.initials: SL
authors.lastname: Fan
authors.forename: Nina
authors.initials: N
authors.lastname: Joyce
authors.forename: Gary L
authors.initials: GL
authors.lastname: Horowitz
mesh_terms: D015415:Biomarkers / Q000032:analysis; D016009:Chi-Square Distribution; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis*; D018709:Statistics, Nonparametric; D014193:Trauma Centers / Q000458:organization & administration*; D014481:United States; D014486:United States Food and Drug Administration
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products