Current 9-1-1 call-taking practice shows poor performance for predicting clinical outcomes in two large emergency medical services datasets
Blanchard, IE; Hao, S; Verma, A; Williamson, T; Lang, ES; Doig, CJ; de Montigny, L.
Introduction: Triage of calls to 9-1-1 for medical emergencies determines the level of EMS response. Undertriage can lead to missed emergencies and poor outcomes; overtriage can lead to unnecessary lights-and-siren driving and diminished efficiency. There have been relatively few assessments of the accuracy with which high-acuity patients can be differentiated from low-acuity patients at the time of the 9-1-1 call.
Objective: To evaluate the performance of current practice in Alberta (AB) and Quebec (QC) at predicting patient acuity based on a range of clinical outcomes.
Methods: We analyzed datasets from two large urban EMS systems accounting for 611 125 adult patient-encounters linked to outcomes. Using the area under the ROC curve (AUC), we assessed the performance of the priority assigned at call-taking (dichotomized as high vs low) in predicting poor status on scene (Critical Illness Prediction score [CIP]; high vs low/moderate), paramedic intervention (time-sensitive vs non-time-sensitive), and post-transport morbidity (admission to ICU) and mortality (survival to discharge).
Results: Current practice predicted CIP with an AUC=0.71 in AB and QC; time-sensitive interventions with AB AUC=0.60 and QC AUC=0.66; admission to ICU with AB and QC AUC=0.65; and survival to discharge with AB AUC=0.63 and QC AUC=0.62. The performance was driven by low sensitivity (41–57%) and acceptable specificity (70–74%). Based on the average of the clinical outcomes, for every 1000 high-priority dispatches in each system, 936 AB patients and 961 QC patients did not show signs of high acuity, whereas for every 1000 low-priority ambulance dispatches in each system, 28 AB patients and 15 QC patients did show signs of high acuity.
Conclusion: We found evidence that current practice in both provinces poorly predicted prehospital patient acuity. These results suggest opportunities to improve medical 9-1-1 call-taking, for example through secondary triage by medically trained professionals or machine learning models trained on a caller’s past medical history and healthcare utilization.
Ian Blanchard has worked in Emergency Medical Services (EMS) systems in Canada and the United Kingdom for the last twenty five years in various capacities, including as an Advanced Care Paramedic, quality assurance strategist, and researcher.