Analysis of an Alternative Model of Definitive Care For Low-Acuity Emergency Calls: A Natural Experiment

Emergency medical services (EMS) diversion strategies attempt to limit the impact of low-acuity care on emergency department (ED) crowding, but evidence supporting these strategies is scarce. This study aims to measure the effect of a treat-in-place and alternative destination program on ED transports and EMS utilization. We used a natural experiment study design to measure effects of a pilot prehospital diversion program on ED transport, number of EMS vehicles dispatched, and EMS time on task for low-acuity emergency calls in a midsized urban setting characterized by a high prevalence of health disparities, concentrated poverty, and limited access to primary care between October 2018 and January 2020. We also used direct variable cost to estimate the return on investment attributable to avoided ED visits. Of 3725 calls that met eligibility criteria, the program responded to 1084 (29.1%), with 56.7% of those resulting in an ED visit, compared with 64.6% of the 492 control calls that were eligible but were dispatched when program services were unavailable. Of 1084 calls receiving response, 213 (19.6%) were enrolled in the program, and 8.5% of those were transported by EMS to the ED. Adjusted results show EMS time on task was 23.4 min less for enrolled calls vs. controls. The program can achieve a positive return on investment by enrolling 2.9 patients/day. A prehospital diversion program reduced ED visits and EMS transport times. Improved targeting of patients for enrollment would further increase the intervention’s efficacy and cost savings.