Low-Acuity Patients Delay High-Acuity Patients in an Emergency Department

Low-Acuity Patients Delay High-Acuity Patients in an Emergency Department

By Mohsen Bayati, Sara Kwasnick, Danqi Luo, Erica Plambeck
2017Working Paper No. 3281

This paper provides empirical evidence that in an ED, arrival of an additional low-acuity patient significantly increases high-acuity patients’ wait times. To estimate that effect, we propose a method motivated by queueing theory and involving quasi-randomization in the wait time forecast at triage for low-acuity patients, which influences their propensity to leave without being seen. That small quasi-randomization (which is inexpensive to implement and poses little or no risk to patients) corrects a large bias in observational data. Empirically and using queueing theory, we identify mechanisms by which a low-acuity patient delays high-acuity patients: pre-triage delay and transition delay in preemption. Thus we identify ways to reduce high-acuity patients’ wait times: to limit preemption; to reduce the standard deviation or mean transition delay; to reduce unnecessary utilization of ED resources by low-acuity patients, e.g., by treating them outside beds or nudging ones that don’t need emergency treatment to choose to leave.