title: Emergency department imaging: are weather and calendar factors associated with imaging volume?
abstract: OBJECTIVE
  To identify weather and calendar factors that would enable prediction of daily emergency department (ED) imaging volume to aid appropriate scheduling of imaging resources for efficient ED function.
  
  
  METHODS
  Daily ED triage and imaging volumes for radiography, computed tomography (CT), and ultrasound were obtained from hospital databases for the period between January 2011 and December 2013 at a large tertiary urban hospital with a Level II trauma centre. These data were tabulated alongside daily weather conditions (temperature, wind and precipitation), day of week, season, and holidays. Multivariate analysis was performed. Pearson correlations were used to measure the association between number of imaging studies performed and ED triage volume.
  
  
  RESULTS
  For every additional 50 triaged patients, the odds of having high (imaging volume ≥90th percentile) radiography, CT, and ultrasound volume increased by 4.3 times (p<0.001), 1.5 times (p=0.02), and 1.4 times (p=0.02), respectively. Tuesday was an independent predictor of high radiography volume (odds ratio=2.8) and Monday was an independent predictor of high CT volume (odds ratio=3.0). Weekday status was an independent factor increasing the odds of a high US volume compared to Saturday (odds ratios ranging from 5.6-9.8). Weather factors and other calendar variables were not independent predictors of high imaging volume. Using Pearson correlations, ED triage volume correlated with number of radiographs, CT, and ultrasound examinations with r=0.73, 0.37, and 0.41, respectively (p<0.0001).
  
  
  CONCLUSIONS
  As ED triage volume was found to be the only factor associated with imaging volume for all techniques, analysis of predictors of ED triage volumes at a particular healthcare facility would be useful to determine imaging needs. Although calendar and weather factors were found to be minor or non-significant independent predictors of ED imaging utilisation, these may be important in influencing the actual number of ED triages.
authors.affiliation: Department of Radiology, Division of Emergency Radiology, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210 Street, Bronx, NY 10467, USA.
authors.forename: K
authors.initials: K
authors.lastname: Burns
authors.affiliation: Department of Radiology, Division of Emergency Radiology, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210 Street, Bronx, NY 10467, USA.
authors.forename: V
authors.initials: V
authors.lastname: Chernyak
authors.affiliation: Department of Radiology, Division of Emergency Radiology, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210 Street, Bronx, NY 10467, USA. Electronic address: mscheinf@montefiore.org.
authors.forename: M H
authors.initials: MH
authors.lastname: Scheinfeld
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000072437:Calendars as Topic / Q000706:statistics & numerical data*; D002648:Child; D002675:Child, Preschool; D003952:Diagnostic Imaging / Q000706:statistics & numerical data*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006786:Hospitals, Urban / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011859:Radiography / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data; D014218:Triage / Q000706:statistics & numerical data*; D014463:Ultrasonography / Q000706:statistics & numerical data; D014887:Weather; D055815:Young Adult