We examined the accuracy of data on unintentional firearm fatalities in the United States. We began with data from the National Violent Death Reporting System (NVDRS) and examined every firearm death reported as an accident by any NVDRS data source - the NVDRS abstracter, the State Vital Statistics Registry (i.e., the ICD-10 Underlying Cause of Death code and manner of death from the death certificate), the medical examiner or coroner report, and the police Supplementary Homicide Report. After carefully reading the information from all sources, we then classified each case as either unintentional or intentional using NVDRS definitions. Comparing our classification with that of the NVDRS abstracter, we conclude that NVDRS data accurately report unintentional firearm deaths (sensitivity 98%; positive predictive value [PPV] 99%). We then compared our classification with that of the State Vital Statistics Registry based on the ICD-10 Underlying Cause of Death code and found great inaccuracy (sensitivity 62%; PPV 58%). Thirty-eight percent of true cases were missed and 42% of reported cases were false positives. As has been previously reported in the literature, over half of unintentional shootings that were inflicted by another person were classified as homicides, not accidents. This is a particular problem for the data on young victims. What was unexpected, however, was the opposite problem: we found many unambiguous suicides and homicides that were reported as accidents. We believe this is due to the ICD-10 coding practice of assigning injury deaths to the "accident" category when manner of death is "pending" or left blank. Finally, at the state-level, we compared our overall results for each state and year with the official National Vital Statistics System count (reported on CDC's WONDER website). We found evidence of even greater over-reporting of unintentional firearm deaths there. In answer to the question, "Are there too many or too few unintentional firearm deaths in official mortality data?" the best answer is, "Both." Many true accidents are missed, while many suicides and homicides are mistakenly reported as accidents. By contrast, the NVDRS applies a case definition for unintentional firearm deaths with consistency and accuracy. (C) 2010 Elsevier Ltd. All rights reserved.
