BACKGROUND: This study aimed to determine whether modified shock index (MSI) is associated with mortality that is superior to heart rate, blood pressure, or the shock index (SI) in emergency patients.METHODS: A retrospective database review was performed on 22161 patients who presented to Peking Union Medical College Hospital Emergency Department and received intravenous fluids from January 1 to December 31, 2009. We gathered data of the patients on age, gender, vital signs, levels of consciousness, presenting complaints, and SI and MSI were calculated for all patients.RESULTS: Multivariate regression analysis was performed to determine the correlation between risk factors and outcome. There is a significant correlation between emergency patient mortality rate and patient's vital signs obtained at the triage desk (HR>120 beats/min, systolic BP<90 mmHg, diastolic BP<60 mmHg). MSI is a stronger predictor of emergency patient mortality compared to heart rate and blood pressure alone, whereas SI does not have a significant correlation with emergency patient mortality rate.CONCLUSION: MSI is a clinically significant predictor of mortality in emergency patients. It may be better than using heart rate and blood pressure alone. SI is not significantly correlated with the mortality rate of the emergency patient.