Unspecified injuries on death certificates: a source of bias in injury research.

Protective gear (for example, helmets and bulletproof vests) shields certain body regions from damaging energy. Failure to specify on death certificates the body region and nature of fatal injuries compromises the utility of mortality data for epidemiologic or prevention research. Of fatally injured California motorcyclists, 41% had no specific injuries listed on their death certificates in 1988. To examine the implications of this problem, the authors abstracted 186 coroner's or medical examiner's reports from four California counties with over 60% nonspecific injuries and one county with few such injuries. These data were merged with computerized death certificate files and with the Fatal Accident Reporting System. Among the 99 cases with nonspecific injury codes, 68% had head injuries, 63% had chest injuries, 58% had abdominal injuries, and 58% had extremity injuries. Reporting sensitivity in the four problem counties varied from 36% for head injury to less than 5% for abdominal, spinal, and extremity injury. The association between head injury and failure to wear a helmet was statistically significant using the coroner's diagnoses (p = 0.02), but not using death certificate diagnoses (p = 0.17). The value of mortality data to injury researchers would be enhanced by better reporting of the nature of injury on death certificates.