Comparison of three emergency department triage systems among Thai medical students: A randomized three-period crossover simulation study

INTRODUCTION: In Thailand, the Emergency Severity Index (ESI) and Ministry of Public Health Emergency Department triage system (MOPH) are commonly used, whereas the Thai Rapid Initial Assessment and Grading for Emergency (TRIAGE) system has been newly proposed. Comparative evidence is limited. We compared correct triage as the primary outcome, with under-triage, over-triage, and completion time as secondary outcomes. METHODS: We conducted a randomized three-period crossover simulation study at the Lampang Medical Education Center from October 2025 to January 2026. Fifth- and sixth-year medical students without recent standardized triage reinforcement classified 50 standardized patient cards per system in one of six sequences, with a one-week washout between periods. Multilevel mixed-effects models were used to estimate between-system differences, with adjustment for period, sequence, and academic year. RESULTS: Sixty students completed all periods. No significant overall differences were detected in correct triage across TRIAGE, ESI, and MOPH (63.2%, 64.5%, and 61.8%, respectively), or in under-triage (19.6%, 20.0%, and 18.8%). Among sixth-year students, correct triage differed significantly across systems (global P = 0.004), with higher adjusted probabilities for ESI and TRIAGE than MOPH. Over-triage differed across systems and was highest with MOPH (7.0%), followed by TRIAGE (5.7%) and ESI (4.9%). Completion time was longest with TRIAGE (32.8 minutes), compared with ESI (24.3 minutes) and MOPH (23.2 minutes). CONCLUSION: No significant overall differences in correct or under-triage were detected, but the study was not powered to establish equivalence. MOPH showed higher over-triage, Completion time was longest with TRIAGE. Generalizability to experienced clinicians requires further study. TRIAL REGISTRATION: Thai Clinical Trials Registry (TCTR) TCTR20260316003.