Accuracy of Prehospital Services' Estimated Time to Arrival for Ground Transport to the Emergency Department

Abstract

Background: Emergency medical services (EMS) transporting patients to the emergency department (ED) typically call ahead to provide an estimated time to arrival (ETA). Accurate ETA facilitates ED preparation and resource allotment in anticipation of patient arrival.

Objective: The study purposed to determine the accuracy of ETA provided by EMS ground units.

Methods: We performed a single-center, prospective, observational study of ED patients arriving via EMS ground transport. The primary outcome was the time difference between EMS-reported ETA and actual time of arrival (ATA). The difference between ATA and ETA was compared using the two-sided Wilcoxon Signed-Rank Test. Subgroup analysis was performed to evaluate ETA accuracy for specific types of transports and assess variability by month and time of day.

Results: We included 1176 patient transports in the final analysis. The overall median difference ATA-ETA was 3 min (interquartile range 1-5 min) with a range of -26-48 minutes (Z = -25.139, p < 0.001). EMS underestimated ETA in 961 cases (81.7%), and 94 ETAs (8.0%) were accurate to within 1 min. The largest difference between ATA and ETA occurred between 07:00-07:59 and 16:00-16:59 (5 min, interquartile range 2-7).

Conclusion: Our data demonstrate that prehospital providers underestimate time to ED arrival in most ground transports; however, the median difference between estimated and actual time to arrival is small.

Keywords: emergency medical services; estimated time to arrival; transportation of patients.