How Are Patient Order and Shift Timing Associated with Imaging Choices in the Emergency Department? Evidence From Niagara Health Administrative Data

STUDY OBJECTIVE: We assessed whether the timing and order of patients over emergency shifts are associated with receiving diagnostic imaging in the emergency department and characterized whether changes in imaging are associated with changes in patients returning to the ED. METHODS: In this retrospective study, we used multivariate and instrumental variable regressions to examine how the timing and order of patients are associated with the use of diagnostic imaging. Outcomes include whether a patient receives a radiograph, a computed tomography (CT) scan, an ultrasound, and 7-day bouncebacks to the ED. The variables of interest are time and order during a physician's shift in which a patient is seen. RESULTS: A total of 841,683 ED visits were examined from an administrative database of all ED visits to Niagara Health. Relative to the first patient, the probability of receiving a radiograph, CT, and ultrasound decreases by 6.4%, 9.1%, and 3.8% if a patient is the 15th patient seen during a shift. Relative to the first minute, the probability of receiving a radiograph, CT, or ultrasound increases by 1.9%, 2.7%, and 1.1% if a patient is seen in the 180th minute. Seven-day bounceback rates are not consistently associated with patient order or timing in a shift and imaging orders. CONCLUSION: Imaging in the ED is associated with shift length and especially patient order, suggesting that physicians make different imaging decisions over the course of their shifts. Additional imaging does not translate into reductions in subsequent bouncebacks to the hospital.