Development of a Binary End-of-Event Outcome Indicator for the NEMSIS Public Release Research Dataset

Introduction: Emergency department and hospital discharge status are available for less than 2% of events recorded in the National EMS Information System (NEMSIS) Public Release Research dataset. The purpose of this project was to develop a binary (“dead” vs. “alive”) end-of-event outcome indicator for the NEMSIS dataset. Methods: The data dictionary for the Version 3 NEMSIS dataset was evaluated to identify elements and codes providing information about a patient's end-of-event status—defined as the point at which EMS providers stopped providing care for an encountered patient, whether at the scene of the event or the transport destination. Those element and code combinations were then used to test the criteria using the NEMSIS-2017 dataset. After revising the criteria based on the NEMSIS-2017 results, the final criteria were then applied to the 2018 NEMSIS dataset. To assess representativeness, the characteristics of events with a determinable outcome were compared to those of the entire dataset. To assess accuracy, the end-of-event indicator was compared with the final reported outcome for patients with a known emergency department disposition. Results: Eighteen NEMSIS element and code combinations suggest a patient was likely “dead” at the end of EMS care, and 15 combinations suggest a patient was likely “alive” at the end of EMS care. A binary end-of-event outcome indicator could be determined for 13,045,887 (98.6%) of the 13,229,079 NEMSIS-2018 9-1-1 initiated ground EMS responses in which patient contact was established, and for 132,728 (89.1%) of the 148,963 events with documented cardiac arrest. The characteristics of the events with determinable end-of-event outcomes did not differ from those of the full dataset. Among patients with a known outcome, 99.6% of those with an “alive” end-of-event indicator were in fact alive at the time of emergency department disposition. Conclusion: A binary end-of-event outcome indicator can be determined for 98.6% of 9-1-1 initiated ground EMS scene responses and 89.1% of cardiac arrests included in the NEMSIS dataset. The events with a determinable outcome appear representative of the larger dataset and the end-of-event indicators are generally consistent with reported emergency department outcomes.