Studies of trauma patients at clinical facilities commonly are flawed because nothing is known about kinetic or other energy forces causing injuries, and analysis may be limited only to inpatients, with no knowledge about those not injured, those with injuries not requiring treatment, those seen only in the emergency department, or those who died at the scene. Such problems are exacerbated in studies from trauma centers, whose populations reflect additional triage. Where alcohol is involved, acute intoxication may cause erroneous AIS, ISS, and Glasgow Coma Scale ratings based on initial patient assessment. Also, selective differences in frequency of testing for alcohol among different categories of patients can alter results.