title: Validation of a tool predicting important findings on computed tomography among Crohn's disease patients.
abstract: BACKGROUND
  Patients with Crohn's disease (CD) are frequently subjected to computed tomography (CT) in the emergency department (ED). This young population is at higher risk of malignancy from radiation exposure.
  
  
  OBJECTIVE
  We aimed to validate a decision tool predicting complications (perforation, abscess or other serious finding) on imaging at two sites.
  
  
  METHODS
  We conducted a retrospective review of CT outcomes among patients with CD with ED visits at two tertiary care centers. Inclusion criteria were a CT of the abdomen/pelvis with contrast and complete lab data (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) within 24 hours of arrival at the University of Michigan (UM) (2012-2013) and the University of Pittsburgh (UPMC) (2009-2012). Sensitivity, negative predictive value (NPV), miss rate and CT avoidance rate were calculated.
  
  
  RESULTS
  At UPMC (n= 210), the tool had a sensitivity of 88.9% and NPV of 98.0%, potentially saving 47.1% from CT with a miss rate of 1.0%. At UM (n= 248), the tool had a sensitivity of 90.9% and NPV of 96.0%, saving 40.3% from CT with a miss rate of 1.6%.
  
  
  CONCLUSIONS
  A decision tool using CRP and ESR predicting CT outcomes among CD patients performed well in an external validation, allowing providers to forgo CT use with a low miss rate.
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA; Veteran's Affairs Hospital, Ann Arbor, MI, USA.
authors.forename: Shail M
authors.initials: SM
authors.lastname: Govani
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA; Veteran's Affairs Center for Clinical Management Research, Ann Arbor, MI, USA.
authors.forename: Akbar K
authors.initials: AK
authors.lastname: Waljee
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Keith E
authors.initials: KE
authors.lastname: Kocher
authors.affiliation: Department of Internal Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Swoger
authors.affiliation: Department of Bioinformatics, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Saul
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Peter Dr
authors.initials: PD
authors.lastname: Higgins
keywords: Computed tomography; over-utilization; radiation; validation