​Duncan K, McMullan C, Mills B. Early warning systems: The next level of rapid response. Nursing2012. 2012 Feb;42(2):38-44.

An early warning system (EWS) is a physiologic scoring system typically used in general medical-surgical units before patients experience a catastrophic medical event. This scoring is accompanied by a descriptive step-by-step guide or algorithm of actions to take based on the patient's assessment score. An EWS can add another layer of early detection to the Rapid Response Team system, helping staff recognize high-risk patients before their condition deteriorates.