A prospective observational approach is chosen as it will allow direct access to information and better capture of the systems being assessed in the ED. Information about each patient's perceived risk at presentation (in terms of the five proposed systems) will be collected at the time of presentation. Information will include rating on the five proposed systems and a number of outcome variables, all of which are recorded as part of routine clinical practice. All information will be captured directly into a specially designed database including a study number to preclude the need to record any personal identifiable information for the study.