Selecting ambulatory emergency care (AEC) patients from the medical emergency in-take: the derivation and validation of the Amb score.

Accurate prediction of the likelihood of same-day discharge could make it possible to direct one-third of the medical in-take to an ambulatory care unit, thereby facilitating bed management. In Phase 1 of this study, we identified seven independent factors that contribute to an ambulatory care score (Amb score) that can potentially be used as a tool to select ambulatory emergency care (AEC) patients from the medical emergency in-take. A high score was associated with discharge within 12 hours of assessment and treatment in hospital. In Phase 2, we verified and internally validated the performance of the Amb score in a different cohort of patients, finding that it functioned well in identifying early discharges (ie AEC patients), with an area under the receiver operator curve (AUROC) of 0.91 (95% CI 0.88-0.94). An Amb score of > or = 5 has a sensitivity of 96% (95% CI 90-98) and a specificity of 62% (95% CI 55-68) in identifying potential AEC patients.