The increasing worldwide demand for ambulance transport may worsen patient prognosis due to a prolonged response time and overcrowding in the emergency department. Triage in the prehospital setting may reduce the demand for ambulance transport by advising low-acuity patients seek non-emergency medical care. In Japan, a five-level triage system that allows emergency medical services (EMS) to triage patients has been implemented since 2014. This study aimed to validate the five-level triage system.

We conducted a retrospective cohort study in patients aged ≥16 years who were transported by EMS to a tertiary-care hospital in Japan from April 2018 to June 2018. We used admission to the intensive care unit (ICU) as the primary outcome. Our secondary outcome was overall admission. We conducted multivariable logistic regression analysis to determine the strength of association between triage acuity and admission (ICU and overall).

A total of 1261 patients were included in the analysis. The odds ratios of ICU admission were 9.62 (95% confidence interval: 5.66–16.3) in Level 1 and 2.93 (95% confidence interval: 1.60–5.38) in Level 2 compared with reference groups composed of Levels 4 and 5. Similar associations were found for triage acuity and overall admission.

Our study validates the five-level prehospital triage system for patients transported by EMS and demonstrates an association between the triage acuity and ICU admissions.