title: A simple decision rule including D-dimer to reduce the need for computed tomography scanning in patients with suspected pulmonary embolism.
abstract: BACKGROUND
  An 'unlikely' clinical decision rule with a negative D-dimer result safely excludes pulmonary embolism (PE) in 30% of presenting patients. We aimed to simplify this diagnostic approach and to increase its efficiency.
  
  
  METHODS
  Data for 723 consecutive patients with suspected PE were analyzed (prevalence of PE, 22%). After constructing a logistic regression model with the D-dimer test result and items from the Wells' score, we identified the most prevalent combinations of influential items and selected new D-dimer positivity thresholds. The performance was separately validated with data from 2785 consecutive patients with suspected PE.
  
  
  RESULTS
  Three Wells items significantly added incremental value to the D-dimer test: hemoptysis, signs of deep vein thrombosis and 'PE most likely'. Based on the most frequent combinations of these three items, we identified two groups: (i) none of these three items positive (41%); (ii) one or more of these items positive (59%). When applying a 1000 μg/L D-dimer threshold in group 1 and 500 μg/L in group 2, PE could be excluded without CT scanning in 36%, at a false-negative rate of 1.2% (95%, 0.04-3.3%). In the validation set, these proportions were 46% and 1.9% (95% CI, 1.2-2.7%), respectively. Using the conventional Wells score with a normal D-dimer result, these rates were, respectively, 22% and 0.6% (95% CI, 0.10-2.4%).
  
  
  CONCLUSIONS
  Combining Wells items with the D-dimer test resulted in a simplified decision rule, which reduces the need for CT scanning in patients with suspected PE. A prospective validation is required before it can be implemented in clinical practice.
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Es
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: L F M
authors.initials: LF
authors.lastname: Beenen
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: R A
authors.initials: RA
authors.lastname: Douma
authors.affiliation: Section of Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: P L
authors.initials: PL
authors.lastname: den Exter
authors.affiliation: Section of Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: I C M
authors.initials: IC
authors.lastname: Mos
authors.affiliation: Department of Internal Medicine, Rijnstate Hospital, Arnhem, the Netherlands.
authors.forename: H A H
authors.initials: HA
authors.lastname: Kaasjager
authors.affiliation: Section of Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: M V
authors.initials: MV
authors.lastname: Huisman
authors.affiliation: Department of Vascular Medicine, University Medical Center, Groningen, the Netherlands.
authors.forename: P W
authors.initials: PW
authors.lastname: Kamphuisen
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Middeldorp
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
authors.forename: P M M
authors.initials: PM
authors.lastname: Bossuyt
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D015415:Biomarkers / Q000097:blood; D015897:Comorbidity; D003661:Decision Support Techniques; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006469:Hemoptysis / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009426:Netherlands / Q000453:epidemiology; D018579:Patient Selection; D011237:Predictive Value of Tests; D015995:Prevalence; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D014057:Tomography, X-Ray Computed; D020246:Venous Thrombosis / Q000175:diagnosis / Q000453:epidemiology
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D
keywords: D-dimer; diagnostic test; pulmonary embolism; tomography scanners, X-ray computed; venous thromboembolism