title: Does a clinical decision rule using D-dimer level improve the yield of pulmonary CT angiography?
abstract: OBJECTIVE
  The objective of our study was to evaluate the impact of incorporating a mandatory clinical decision rule and selective d-dimer use on the yield of pulmonary CT angiography (CTA).
  
  
  METHODS
  Guidelines incorporating a clinical decision rule (Wells score: range, 0-12.5) and a highly sensitive d-dimer assay as decision points were placed into a computerized order entry menu. From December 2006 through November 2008, 261 pulmonary CTA examinations of 238 men and 14 women (mean age ± SD, 65 ± 12 years; range, 31-92 years) were performed. Eight patients underwent more than one pulmonary CTA examination. Charts were reviewed. The results of pulmonary CTA, the clinical decision rule, and d-dimer level (if obtained) were analyzed with the Student t test, chi-square test, or other comparisons using statistical software (MedCalc, version 11.0).
  
  
  RESULTS
  Of the pulmonary CTA examinations, 16.5% (43/261) were positive for pulmonary embolism (PE) compared with 3.1% (6/196) during the previous 2 years. The mean clinical decision rule score and mean d-dimer level were 5.5 ± 2.4 (SD) and 4956 ± 2892 ng/mL, respectively, for those with PE compared with 4.5 ± 2.1 and 2398 ± 2100 ng/mL for those without PE (both, p < 0.01). The negative predictive value of a clinical decision rule score of 4 or less and d-dimer level of less than 1000 ng/mL was 1.0. A clinical decision rule of greater than 4 and a higher d-dimer level were better predictors for PE, especially a d-dimer level of greater than 3000 ng/mL (odds ratio = 6.69; 95% CI = 2.72-16.43).
  
  
  CONCLUSIONS
  Guidelines combining a clinical decision rule with d-dimer level significantly improved the utilization of pulmonary CTA and positive yield for PE.
authors.affiliation: Pulmonary and Critical Care Section, West Los Angeles Medical Center, CA 90073, USA. Guy.Soohoo@va.gov
authors.forename: Guy W Soo
authors.initials: GW
authors.lastname: Hoo
authors.forename: Carol C
authors.initials: CC
authors.lastname: Wu
authors.forename: Sondra
authors.initials: S
authors.lastname: Vazirani
authors.forename: Zhaoping
authors.initials: Z
authors.lastname: Li
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Barack
mesh_terms: D000368:Aged; D000792:Angiography / Q000706:statistics & numerical data; D002985:Clinical Protocols; D015331:Cohort Studies; D003661:Decision Support Techniques; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D019983:Guideline Adherence; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D