title: National trends in use of computed tomography in the emergency department.
abstract: OBJECTIVE
  The role of computed tomography (CT) in acute illnesses has increased substantially in recent years; however, little is known about how CT use in the emergency department (ED) has changed over time.
  
  
  METHODS
  A retrospective study was performed with the 1996 to 2007 National Hospital Ambulatory Medical Care Survey, a large nationwide survey of ED services. We assessed changes during this period in CT use during an ED visit, CT use for specific ED presenting complaints, and disposition after CT use. Main outcomes were presented as adjusted risk ratios (RRs).
  
  
  RESULTS
  Data from 368,680 patient visits during the 12-year period yielded results for an estimated 1.29 billion weighted ED encounters, among which an estimated 97.1 million (7.5%) patients received at least one CT. Overall, CT use during ED visits increased 330%, from 3.2% of encounters (95% confidence interval [CI] 2.9% to 3.6%) in 1996 to 13.9% (95% CI 12.8% to 14.9%) in 2007. Among the 20 most common complaints presenting to the ED, there was universal increase in CT use. Rates of growth were highest for abdominal pain (adjusted RR comparing 2007 to 1996=9.97; 95% CI 7.47 to 12.02), flank pain (adjusted RR 9.24; 95% CI 6.22 to 11.51), chest pain (adjusted RR 5.54; 95% CI 3.75 to 7.53), and shortness of breath (adjusted RR 5.28; 95% CI 2.76 to 8.34). In multivariable modeling, the likelihood of admission or transfer after a CT scan decreased over the years but has leveled off more recently (adjusted RR comparing admission or transfer after CT in 2007 to 1996=0.42; 95% CI 0.32 to 0.55).
  
  
  CONCLUSIONS
  CT use in the ED has increased significantly in recent years across a broad range of presenting complaints. The increase has been associated with a decline in admissions or transfers after CT use, although this effect has stabilized more recently.
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI, USA. kkocher@umich.edu
authors.forename: Keith E
authors.initials: KE
authors.lastname: Kocher
authors.forename: William J
authors.initials: WJ
authors.lastname: Meurer
authors.forename: Reza
authors.initials: R
authors.lastname: Fazel
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Scott
authors.forename: Harlan M
authors.initials: HM
authors.lastname: Krumholz
authors.forename: Brahmajee K
authors.initials: BK
authors.lastname: Nallamothu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D021501:Flank Pain; D019538:Health Care Surveys; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data* / Q000639:trends; D014481:United States; D055815:Young Adult