Predicting Hospital Admission among High Acuity Triaged Patients Transported to the Emergency Department in Ontario, Canada: A Population-Based Cohort Study using Machine Learning

Abstract Background Paramedics are mandated to transport emergently triaged patients to the closest emergency department (ED). The closest ED may not be the optimal transport destination if further distanced ED’s can provide specialized care or are less crowded. Machine learning may support paramedic decision-making to transport a specific subgroup of emergently triaged patients that are unlikely to require hospital admission or emergency care to a more appropriate ED. We examined whether prehospital patient characteristics known to paramedics were predictive of hospital admission. Methods We conducted a retrospective cohort study using machine learning algorithms to analyze ED visits of the National Ambulatory Care Reporting System from Jan 1, 2018 to Dec 31, 2019 in Ontario, Canada. We included all adult (≥ 18 years) paramedic transports to the ED who had an emergent Canadian Triage Acuity Scale score (CTAS 2). Eight prehospital characteristic classes known to paramedics were used. We applied four machine learning algorithms that were trained and assessed using 10-fold cross-validation to predict the ED visit disposition of admission to hospital or discharged from ED. Predictive model performance was determined using the area under the receiving operating characteristic curve (AUC) with 95% confidence intervals and probabilistic accuracy using the Brier Scaled score. Variable importance scores were computed to determine the top 10 predictors of hospital admission. We also reported sensitivity, specificity, and positive and negative predictive values to support performance interpretation. Results All machine learning algorithms performed similarly for the prediction of which ED patient visits would be admitted to hospital (AUC 0.77–0.78, Brier Scaled 0.22–0.24). The characteristics most predictive of admission included age 65 to 105 years, referral source from a residential care facility, presenting with a respiratory complaint, and receiving home care. Conclusions Machine learning algorithms performed well in predicting ED visit dispositions using a comprehensive list of prehospital patient characteristics. To the best of our knowledge, this study is the first to utilize machine learning to predict ED visit outcomes from patient characteristics known prior to paramedic transport. This study has potential to inform paramedic regulations regarding the distribution of emergently triaged patients.

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