title: The association between advanced diagnostic imaging and ED length of stay.
abstract: OBJECTIVE
  There has been a rise in advanced diagnostic imaging (ADI) use in the emergency department (ED). Increased utilization may contribute to longer length of stay (LOS), but prior reports have not considered improved methods for modeling skewed LOS data.
  
  
  METHODS
  The 2010 National Hospital Ambulatory Medical Care Survey data were analyzed by 5 common ED chief complaints. Generalized linear model (GLM) was compared to quantile and ordinary least squares (OLS) regression to evaluate the association between ADI and ED LOS. Receipt of computed tomography or magnetic resonance imaging was the primary exposure. Emergency department LOS was the primary outcome.
  
  
  RESULTS
  Of the 33,685 ED visits analyzed, 17% involved ADI. The median LOS for patients without ADI was 138 minutes compared to 252 minutes for those who received ADI. Overall, GLM offered the most unbiased estimates, although it provided similar adjusted point estimates to OLS for the marginal change in LOS associated with ADI. The effect of imaging differed by LOS quantile, especially for patients with abdominal pain, fever, and back symptoms.
  
  
  CONCLUSIONS
  Generalized linear model offered an improved modeling approach compared to OLS and quantile regression. Consideration of such techniques may facilitate a more complete view of the effect of ADI on ED LOS.
authors.affiliation: Robert Wood Johnson Foundation Clinical Scholars program, US Department of Veterans Affairs, Emergency Medicine Center, University of California Los Angeles, 10940 Wilshire Blvd, Suite 710, Los Angeles, CA. Electronic address: hkanzaria@mednet.ucla.edu.
authors.forename: Hemal K
authors.initials: HK
authors.lastname: Kanzaria
authors.affiliation: Emergency Medicine K12 Scholar, Department of Emergency Medicine, Mount Sinai Medical Center.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Probst
authors.affiliation: Department of Health Policy and Management, University of California Los Angeles, Fielding School of Public Health, UCLA Center for Health Policy Research.
authors.forename: Ninez A
authors.initials: NA
authors.lastname: Ponce
authors.affiliation: Department of Emergency Medicine, University of California San Francisco, San Francisco General Hospital.
authors.forename: Renee Y
authors.initials: RY
authors.lastname: Hsia
mesh_terms: D015746:Abdominal Pain / Q000175:diagnosis*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001416:Back Pain / Q000175:diagnosis*; D002637:Chest Pain / Q000175:diagnosis*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D005334:Fever / Q000175:diagnosis*; D006261:Headache / Q000175:diagnosis*; D006801:Humans; D016018:Least-Squares Analysis; D007902:Length of Stay / Q000706:statistics & numerical data*; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D055815:Young Adult