Motor Vehicle Crash Case Definitions and How They Impact Injury Surveillance

BACKGROUND Motor vehicle crashes are a leading cause of injury in North Carolina. Motor vehicle crash injury surveillance that relies on hospital diagnostic codes alone may underestimate injury. Our objective was to describe how motor vehicle crash injury case definitions can impact results when using hospital data.METHODS We received motor vehicle crash-related emergency department visits from 1 large metropolitan county in North Carolina for the year 2013. Emergency department visits were categorized based on 3 mutually exclusive case definitions: motor vehicle crash injuries identified using external cause-of-injury codes, text searches for motor vehicle crash-related key words in triage notes or chief complaint fields, and motor vehicle crash injuries identified using both text searches and external cause-of-injury codes. Descriptive statistics were used to examine differences in patient characteristics according to case definition.RESULTS Most emergency department visits contained both motor vehicle crash text and motor vehicle crash external cause-of-injury codes (N = 13,422, 76%). Patients identified using external cause-of-injury codes only were more likely to be male, arrive by ambulance, and be admitted to the hospital compared to patients identified by text searches or both text and external cause-of-injury codes. Twenty-eight percent of the patients (N = 5,021) received non-injury related diagnoses in the emergency department. Among these patients, the most frequently used first diagnoses were for vague or chronic pain conditions.LIMITATIONS We relied on secondary data and were unable to perform medical chart reviews; hospital data have limited information surrounding the crash event.CONCLUSION The choice of case definition used for motor vehicle crash surveillance impacts the picture of motor vehicle crash injury severity. It is important for researchers to be aware of the impact case definition has on their results.