title: Reduction in observation unit length of stay with coronary computed tomography angiography depends on time of emergency department presentation.
abstract: OBJECTIVE
  Prior studies demonstrating shorter length of stay (LOS) from coronary computed tomography angiography (CCTA) relative to stress testing in emergency department (ED) patients have not considered time of patient presentation. The objectives of this study were to determine whether low-risk chest pain patients receiving stress testing or CCTA have differences in ED plus observation unit (OU) LOS and if there are disparities in testing modality use, based on the time of patient presentation to the ED.
  
  
  METHODS
  The authors examined a cohort of low-risk chest pain patients evaluated in an ED-based OU using prospective and retrospective OU registry data. During the study period, stress testing and CCTA were both available from 08:00 to 17:00 hours. CCTA was not available on weekends, and therefore only subjects presenting on weekdays were included. Cox regression analysis was used to model the effect of testing modality (stress testing vs. CCTA) on OU LOS. Separate models were fit based on time of patient presentation to the ED using 4-hour blocks beginning at midnight. The primary independent variable was testing modality: stress testing or CCTA. Age, sex, and race were included as covariates. Logistic regression was used to model testing modality choice by time period adjusted for age, sex, and race.
  
  
  RESULTS
  Over the study period, 841 subjects presented Monday through Friday. Median LOS was 18.0 hours (interquartile range [IQR] = 11.7 to 22.9 hours). Objective cardiac testing was completed in 788 of 841 (94%) patients, with 496 (63%) receiving stress testing and 292 (37%) receiving CCTA. After age, race, and sex were adjusted for, patients presenting between 08:00 and 11:59 hours not only had a shorter LOS associated with CCTA (p < 0.0001), but also had a greater likelihood of being tested by CCTA (p = 0.001). None of the other time periods had significant differences in LOS or testing modality choice for CCTA relative to stress testing.
  
  
  CONCLUSIONS
  In an OU setting with weekday and standard business hours CCTA availability, CCTA testing was associated with shorter LOS among low-risk chest pain patients only in patients presenting to the ED between 08:00 and 11:59 hours. That time period was also associated with a greater likelihood of being tested by CCTA, suggesting that ED providers may have intuited the inability of CCTA to shorten LOS during other times.
authors.affiliation: Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA. smahler@wfubmc.edu
authors.forename: Simon A
authors.initials: SA
authors.lastname: Mahler
authors.forename: Brian C
authors.initials: BC
authors.lastname: Hiestand
authors.forename: Jamaji
authors.initials: J
authors.lastname: Nwanaji-Enwerem
authors.forename: David C
authors.initials: DC
authors.lastname: Goff
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Burke
authors.forename: L
authors.initials: L
authors.lastname: Douglas Case
authors.forename: Bret
authors.initials: B
authors.lastname: Nicks
authors.forename: Chadwick D
authors.initials: CD
authors.lastname: Miller
mesh_terms: D000328:Adult; D002637:Chest Pain / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D017023:Coronary Angiography / Q000379:methods / Q000706:statistics & numerical data*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D004632:Emergency Medical Services / Q000458:organization & administration; D004638:Emergency Treatment / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009657:North Carolina; D010351:Patient Discharge / Q000706:statistics & numerical data; D011446:Prospective Studies; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000706:statistics & numerical data*; D014481:United States