Objective An ideal emergency department (ED) triage system accurately prioritises patients on the basis of the urgency of interventions required to avoid under- or over-triage. The objective of this study was to develop and validate a five-level Taiwan triage and acuity scale (TTAS) with an electronic decision support tool.

Methods This prospective, multicentre, observational study included 10533 patients triaged at 11 academic medical centres, 18 regional and four district hospitals. Adult patients presenting to the ED were independently triaged by the duty triage nurse in the usual way and trained research nurses using TTAS with a computerised decision support system. Weighted κ statistics were used to assess the reproducibility. Hospitalisation, length of stay, and medical resource consumption were analysed by TTAS acuity levels.

Results Most cases were stratified into levels 2 to 3 by the existing four-level triage system, whereas the TTAS stratified most patients to levels 3 (41.4%) and 4 (25.0%), and only a small number to level 1 (3.9%) (resuscitation; most urgent). Weighted κ for TTAS assignment was 0.87 (95% CI 0.85 to 0.89). The decrease in mean medical resource consumption and hospitalisation rate was statistically significant with each decrease in the TTAS triage acuity level. The length of stay also decreased significantly as the TTAS level acuity fell from levels 2 to 5.

Conclusions The TTAS was found to be a reliable triage system that accurately prioritises the treatment needed to avoid overtriage, more efficiently deploying the appropriate resources to ED patients.