Field triage systems: methodologies from the literature

The primary goal of the Neely Conference project is to work toward defining a set of research criteria for medical necessity in emergency medical services (EMS). This paper reviews the extant literature on triage and nontransport decisions made in the field by EMS personnel, with emphasis on the methodologies that have been used to date. Two types of medical necessity standards are considered. First, there are triage criteria for determining whether a given patient requires EMS transport to the hospital, or whether an alternative might be appropriate. These triage criteria might be incorporated into protocols that field personnel could apply on scene to determine the best disposition for a given patient. Second, there are the outcome measures against which the decisions made by the field personnel are judged. In some cases, the outcome measure is the judgment of a reviewing emergency physician or nurse, while in others specific outcome measures are used to judge the performance of the criteria and the decision making of the field providers. While review of the literature shows that no "standard" set of triage criteria have been generated or validated in determining medical necessity in EMS, there are certain themes that emerge from the literature, and these themes can likely form the basis of a consensus on elements of a medical necessity criteria that need to be validated and refined. These may include (for triage criteria) vital signs, chief complaints, and physical exam findings, and (for outcome measures) hospital admission, critical events, death, and diagnosis.