title: Negative D-dimer testing excludes pulmonary embolism in non-high risk patients in the emergency department.
abstract: OBJECTIVE
  The purpose of this study was to assess the ability of d-dimer testing to obviate the need for cross-sectional imaging for patients at "non-high risk" for pulmonary embolism (PE).
  
  
  METHODS
  This is a retrospective study of emergency department patients at an academic medical center who underwent cross-sectional imaging (MRA or CTA) to evaluate for PE from 2008 to 2013. The primary outcome was the NPV of d-dimer testing when used in conjunction with clinical decision instruments (CDIs = Wells', Revised Geneva, and Simplified Revised Geneva Scores). The reference standard for PE status included image test results and a 6-month chart review follow-up for venous thromboembolism as a proxy for false negative imaging. Secondary analyses included ROC curves for each CDI and calculation of PE prevalence in each risk stratum.
  
  
  RESULTS
  Of 459 patients, 41 (8.9%) had PE. None of the 76 patients (16.6%) with negative d-dimer results had PE. Thus, d-dimer testing had 100% sensitivity and NPV, and there were no differences in CDI performance. Similarly, when evaluated independently of d-dimer results, no CDI outperformed the others (areas under the ROC curves ranged 0.53-0.55). There was a significantly higher PE prevalence in the high versus "non-high risk" groups when stratified by the Wells' Score (p = 0.03).
  
  
  CONCLUSIONS
  Negative d-dimer testing excluded PE in our retrospective cohort. Each CDI had similar NPVs, whether analyzed in conjunction with or independently of d-dimer results. Our results confirm that PE can be safely excluded in patients with "non-high risk" CDI scores and a negative d-dimer.
authors.affiliation: BerbeeWalsh Department of Emergency Medicine, University of Wisconsin-Madison, 800 University Bay Drive, Suite 310, Mail Code 9123, Madison, WI, 53705, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Harringa
authors.affiliation: BerbeeWalsh Department of Emergency Medicine, University of Wisconsin-Madison, 800 University Bay Drive, Suite 310, Mail Code 9123, Madison, WI, 53705, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Bracken
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, USA.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Nagle
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, USA.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Schiebler
authors.affiliation: BerbeeWalsh Department of Emergency Medicine, University of Wisconsin-Madison, 800 University Bay Drive, Suite 310, Mail Code 9123, Madison, WI, 53705, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Pulia
authors.affiliation: BerbeeWalsh Department of Emergency Medicine, University of Wisconsin-Madison, 800 University Bay Drive, Suite 310, Mail Code 9123, Madison, WI, 53705, USA.
authors.forename: James E
authors.initials: JE
authors.lastname: Svenson
authors.affiliation: BerbeeWalsh Department of Emergency Medicine, University of Wisconsin-Madison, 800 University Bay Drive, Suite 310, Mail Code 9123, Madison, WI, 53705, USA. mdreppli@medicine.wisc.edu.|Department of Radiology, University of Wisconsin-Madison, Madison, USA. mdreppli@medicine.wisc.edu.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Repplinger
mesh_terms: D000328:Adult; D000072226:Computed Tomography Angiography; D003661:Decision Support Techniques; D004636:Emergency Service, Hospital; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000097:blood* / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D
keywords: CT; Clinical decision instruments; D-dimer; MRI; Pulmonary embolism