Validation of the Emergency Severity Index (ESI) in self-referred patients in a European emergency department

OBJECTIVE: To validate the Emergency Severity Index (ESI) triage algorithm in predicting resource consumption and disposition by self-referred patients in a European emergency department. METHODS: This was a prospective, observational cohort study using a convenience sample of self-referred emergency department patients >14 years of age presenting to a busy urban teaching hospital during a 39-day period (27 May-4 July 2001). Observed resource use was compared with resource utilisation predicted by the ESI. Outpatient referrals after discharge and hospitalisations were also recorded. RESULTS: ESI levels were obtained in 1832/3703 (50%) self-referred patients, most of whom were in the less severe ESI-4 (n = 685, 37%) and ESI-5 (n = 983, 54%) categories. Use of resources was strongly associated with the triage level, rising from 15% in ESI-5 to 97% in ESI-2 patients. Specialty consultations and admissions also rose with increasing ESI severity. Only 5% of ESI-5 patients required consultation and <1% were admitted, whereas 85% of ESI-2 patients received a consultation and 56% were admitted, 26% to a critical care bed. Only 2% of the ESI-5 patients underwent blood tests, compared with 76% of the sicker ESI-2 patients. X rays were the most commonly used resource in patients triaged to ESI-4 and ESI-5. CONCLUSION: The ESI triage category reliably predicts the severity of a patient's condition, as reflected by resource utilisation, consultations and admissions in a population of self-referred patients in a European emergency department. It clearly identifies patients who require minimal resources, or at most an x ray, and those unlikely to require admission.