Background The 8^th regional health area of Thailand, have 7 province and 88 hospitals. Three phase triage, first at dispatch centre second on scene and third in emergency room (ER) were done by difference registered nurses (RN). One patient will be 3 times triage by 3 difference RN.

Methods This Quasi-experimental study focus on agreement of triage result by RN from 88 hospitals, compared between before and after triage training. RN was practically trained, triage competency development for modified Emergency Severity Index (ESI), on June 2014. The data was collected on May and July 2014. Analysed by kappa statistics and 95% CI: of kappa. The percent agreement before and after training triage was compared by Chi-square test.

Results 3,325 patients were triaged, almost triage level were yellow and red. There were 24 Clinical-based categories of Emergency service. Top three of the Categories were Motor Vehicle Accident (22.20%) Sick (17.75%) Unconscious (8.30%). Before training, the agreement between dispatch and scene was almost perfect with kappa 0.82 (95% CI: = 0.78–0.87) the agreement between scene and ER was moderate with kappa 0.47 (95% CI: = 0.42–0.52). After training, the agreement between dispatch and scene was almost perfect with kappa 0.85 (95% CI: = 0.80–0.89) the agreement between scene and ER was moderate with kappa 0.57 (95% CI: = 0.52–0.61). The percent agreement of dispatch and scene triage between before and after training were not different. But the percent agreement of scene and ER triage were significantly improved (P-value = 0.001),with 0.05 level of significance.

Conclusions The agreement of scene and ER triage was moderate, since patients were received first aid and treatment in transit that did change for level of triage when they came to ER. But after training, this agreement was better than before. This study confirm that we can improve triage agreement for RN by triage training and we should improve the other first aid and treatment competency for RN.