vened to develop the guidelines for collecting information on outcomes. The consensus panel, at a minimum, should include NCIPC and the Health Resources and Services Administration, in collaboration with the American College of Surgeons' Committee on Trauma, the American Academy of Physical Medicine and Rehabilitation, and the State and Territorial Injury Prevention Directors' Association (see Chapter 6).

Uniform hospital discharge data, currently maintained by 39 states (Annest et al., 1998), are another source of information about injuries resulting in hospitalization, and are most informative when external cause coding is appended to every discharge record. Hospital discharge data systems are particularly well suited for examining the epidemiology of injury-related hospitalizations and for system evaluation, because they maintain information on all hospitalizations regardless of where the patient is treated. Increasingly, they are being used to evaluate the performance of inclusive trauma systems (MacKenzie et al., 1990a; Mullins et al., 1994) and to examine the epidemiology of injury. However, to use these data to estimate the true incidence of injury resulting in hospitalization, one must avoid double counting those patients transferred from one facility to another and those admitted multiple times for treatment of the same injury. Although the percentage of patients transferred is generally low (e.g., less than 3 percent in Maryland), transferred patients represent an important subgroup (MacKenzie et al., 1990b). In most instances, a readmission should be assigned a principal diagnosis that reflects the complication or need for further treatment, with an additional code to indicate the late effect of a particular injury. Increasingly, databases are being constructed to facilitate the identification of readmissions either through the incorporation of an additional field for readmission data or by facilitating the ability to link information on multiple discharges referring to the same person. The committee strongly suggests that additional fields be added to hospital discharge systems to indicate that a patient transferred from another hospital; that the patient is being readmitted for a previous injury; and for the date of the injury.

Although statewide uniform hospital discharge data do not include information on injury deaths that occur in the field or during transport, they have become a valuable source of information for states and local communities. In particular, when linked to vital statistics or medical examiner data, they provide a complete picture of all trauma severe enough to result in death or hospitalization.

The epidemiology of less severe injuries requires data from emergency departments, hospital clinics, and physicians' offices. Nine state have recently established E-coded statewide emergency department record systems, an encouraging trend that can be assisted by the Data Elements for Emergency Department Systems, Release 1.0 (NCIPC, 1997). This new system contains uniform specifications for data entered in emergency department patient records, including external cause-of-injury coding, and incorporates national standards for electronic data interchange. Other state and local data that can be useful in studying



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