ACADEMIC EMERGENCY MEDICINE 2011; 18:822–829 © 2011 by the Society for Academic Emergency Medicine


Objectives:  The objective was to compare the validity of an existing informally structured triage system with the Emergency Severity Index (ESI) and the Manchester Triage System (MTS).

Methods:  A total of 900 patients were prospectively triaged by six trained triage nurses using the three systems. Triage ratings of 421 (48%) patients treated only by emergency department (ED) physicians were compared with a reference standard determined by an expert panel. The percentage of undertriage, the sensitivity, and the specificity for each urgency level were calculated. The relationship between urgency level, resource use, hospitalization, and length of stay (LOS) in the 900 triaged patients was determined.

Results:  The percentage of undertriage using the ESI (86 of 421; 20%) was significantly higher than in the MTS (48 of 421; 11%). When combining urgency levels 4 and 5, the percentage of undertriage was 8% for the informally structured system (ISS), 14% for the ESI, and 11% for the MTS. In all three systems, sensitivity for all urgency levels was low, but specificity for levels 1 and 2 was high (>92%). Sensitivity and specificity were significantly different between ESI and MTS only in urgency level 4. In all 900 patients triaged, urgency levels across all systems were associated with significantly increased resource use, hospitalization rate, and LOS.

Conclusions:  All three triage systems appear to be equally valid. Although the ESI showed the highest percentage of undertriage and the ISS the lowest, it seems preferable to use a verifiable, formally structured triage system.