The impact of clinically undiagnosed injuries on survival estimates.

OBJECTIVES Missed injury diagnoses may cause potentially preventable deaths. To estimate the effect of clinically undiagnosed injuries on injury-specific survival estimates and the accuracy of an injury severity score. To also estimate the potentially preventable mortality attributable to these injuries. DESIGN, SETTING, AND PATIENTS In a nation-wide, population-based study, data were collected from all hospital admissions for injuries in Sweden between 1998 and 2004. We studied 8627 deaths in hospital among 598,137 incident hospital admissions. MEASUREMENTS AND MAIN RESULTS New specific-injury categories were added in 7.4% (95% confidence interval [CI] 6.8-8.0) of all deaths with an autopsy rate of 24.2%. It was estimated that this proportion would have increased to 25.1% (95% CI 23.0-27.2), if all deaths had been autopsied. The most pronounced effect of clinically undiagnosed injuries was found for internal organ injury in the abdomen or pelvis, where they reduced the estimated survival from 0.83 to 0.69 (95% CI for the difference: 0.09-0.20). Autopsy diagnoses also revealed substantial bias of survival estimates for vascular injuries in the thorax and crush injuries to the head. The performance of the International Classification of Diseases Injury Severity Score improved when autopsy diagnoses were added to hospital discharge diagnoses. The maximum proportion of injury deaths attributable to missed injuries was estimated to be 6.5%. CONCLUSIONS Maintaining a high autopsy rate and merging accurate hospital discharge data and autopsy data are effective ways to improve the accuracy of survival estimates and mortality prediction models, and to estimate mortality attributable to diagnostic failures.