Objective This study aims to validate previously reported triage tool titled Sydney Triage to Admission Risk Tool (START+) and investigate whether an extended version of the tool could be used to identify and stream appropriate short stay admissions to ED observation units or specialised short stay inpatient wards.

Methods This was a prospective study at two metropolitan EDs in Sydney, Australia. Consecutive triage encounters were observed by a trained researcher and START scores calculated. The primary outcome was length of stay <48 hours. Multivariable logistic regression was used to estimate area under curve of receiver operator characteristic (AUROC) for START scores. The original START tool was then extended to include frailty and multiple or major comorbidities as additional variables to assess for further predictive accuracy.

Results There were 894 patients analysed during the study period. Of the 894 patients, there were 732 patients who were either discharged from ED or admitted for <2 days. The AUROC for the original START+ tool was 0.80 (95% CI 0.77 to 0.83). The presence of frailty was found to add a further five points and multiple comorbidities added another four points on top of the START score, and the AUROC for the extended START score 0.84 (95% CI 0.81 to 0.88).

Conclusion The overall performance of the extended ED disposition prediction tool that included frailty and multiple medical comorbidities significantly improved the ability of the START tool to identify patients likely to be discharged from ED or require short stay admission <2 days.

Trial registration number ACTRN12618000426280