Leveraging machine learning to identify subgroups of misclassified patients in the emergency department: a multi-center proof-of-concept study.

Background: Hospitals use triage systems to prioritize the needs of patients within available resources. Misclassification of a patient can lead to either adverse outcomes in a patient who did not receive appropriate care in the case of undertriage or waste of hospital resources in the case of overtriage. Recent advances in machine learning algorithms allow for the quantification of variables important to under- and overtriage.

Objective: The aim of this study was to identify clinical features most strongly associated with triage misclassification using a machine learning classification model to capture non-linear relationships.

Methods: Multicenter retrospective cohort data from two big regional hospitals in Norway was extracted. The South African Triage system is used at Bergen University Hospital and the Rapid Emergency Triage and Treatment System is used at Trondheim University Hospital. Variables included triage score, age, gendersex, arrival time, subject area affiliation, reason for emergency department contact, discharge location, level of care, and time of death were retrieved. Random forest classification models were used to identify features with the strongest association with overtriage and undertriage in clinical practice in Bergen and Trondheim. We reported variable importance as SHAP-values (SHapley Additive exPlanations).

Results: We collected data on 205,488 patient records from Bergen University Hospital and 304,997 patient records from Trondheim University Hospital. Overall, overtriage was very uncommon at both hospitals (all <0.1%), with undertriage differing between both locationlocations with 0.8% at Bergen and 0.2% at Trondheim University Hospital. Demographics were similar for both hospitals, however the percentage given a high priority triage score (red or orange) was higher in Bergen (24%) compared to 9% in Trondheim. Clinical referral department was found to be the variable with the strongest association with undertriage (mean SHAP +0.62 and +0.37 for Bergen and Trondheim, respectively).

Conclusions: We identified subgroups of patients consistently undertriaged using two common triage systems. While the importance of clinical characteristics to triage misclassification varies by triage system and location, but we found consistent evidence between the two locations that clinical referral department is the most important variable associated with triage misclassification. Replication of this approach at other centers could help to further improve triage scoring systems and improve patient care worldwide.