Triage and Injury Severity Scores as predictors of mortality and hospital admission for injuries: a validation study.

Background: Many emergency departments use a rating system to establish priority based on urgency: "triage". The aim of this study was to evaluate the validity of triage in predicting hospitalization and mortality compared to that of the ICD-9-CM based Injury Severity Score (ISS).

Sources: The Emergency Information System 2000, the Hospital Information System 2000-2001 and the Mortality Register 2000-2001, of the Lazio Region. Case selection: Emergency department visits for traumas that occurred on the road or at home.

Outcomes: Hospitalization and 30-day mortality. For each case, trauma diagnoses from the ICD-9-CM were given a corresponding ISS value. We performed logistic models, including age, sex and, alternatively, triage or ISS. We compared discrimination measures and calibration of the models.

Results: Out of 264,709 emergency department visits, 22,249 (8.4%) were followed by a hospitalization and 655 (0.2%) died within 30 days. ISS scores were calculated for 72,179 (27%) cases. Of the most urgent triage (840 patients), 78.3% (658) were hospitalized and 9% (76) died, while among patients with ISS > or = 16 value (1276) 36.4% (464) of were hospitalized and 1.8% (23) died. Measures of discrimination and calibration showed similar results. The triage model had a better fitness in predicting hospitalization probability for home accidents (Hosmer-Lemeshow statistic: chi(2)(triage)=5.5 vs chi(2)(ISS)=34.3) and had a better performance for road accidents (ROC(triage)=0.71 vs ROC(ISS)=0.66). There were no differences between the models in predicting the probability of death.

Conclusions: The agreement between the two scales confirms the validity of triage as a clinical management tool in the emergency department, and as a proxy of trauma severity.