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Missing cases of injury death: use of quantitative methods and case reviews to inform future improvements in case definition
  1. Colin Cryer1,
  2. Pauline Gulliver2,
  3. Gabrielle Davie1,
  4. Ari Samaranayaka3,
  5. Christine Fowler4
  1. 1 Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand
  2. 2 School of Population Health, University of Auckland, Auckland, New Zealand
  3. 3 Biostatistics Centre, University of Otago, Dunedin, New Zealand
  4. 4 National Collections and Reporting, Ministry of Health, Wellington, New Zealand
  1. Correspondence to Dr Colin Cryer, Preventive and Socail Medicine, University of Otago, Dunedin 9016, New Zealand; peter.cryer1951{at}


Background Knowledge of fatal injuries is required to inform prevention activities. Where hospital patients with an injury principal diagnosis (PDx) died and were certified to a medical underlying cause of death (UCoD), there is the potential to underestimate injury mortality. We sought to characterise injury/non-injury (NI) mismatches between PDx and UCoD by identifying which subgroups had small/large mismatches, and to understand why mismatches had occurred using informative examples.

Method Hospital records (n=10 234) with a PDx of injury were linked to the mortality collection using a unique personal identifier. Percentages UCoD coded to a NI were tabulated, for three follow-up periods and by selected variables. Additionally, we reviewed a sample of 70 records for which there was a mismatch.

Results %NIs were 39%, 66% and 77% for time from injury to death of <1 week, <90 days and <1 year, respectively. Variations in %NI were found for all variables. Illustrative examples of 70 medical UCoD deaths showed that for 12 cases the injury event was unequivocally judged to have resulted in premature death. A further 16 were judged as injury deaths using balance of probability arguments.

Conclusion There is variation in rates of mismatch between PDx of injury and UCoD of NI. While legitimate reasons exist for mismatches in certain groups, a material number of injury deaths are not captured using UCoD alone; a new operational definition of injury death is needed. Early solutions are proposed. Further work is needed to investigate operational definitions with acceptable false positive and negative detection rates.

  • surveillance
  • mortality
  • indicators
  • epidemiology

Data availability statement

Data was obtained from the New Zealand Ministry of Health and are not publicly available.

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Data availability statement

Data was obtained from the New Zealand Ministry of Health and are not publicly available.

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  • Contributors All authors contributed to the conception of the project. They contributed to the development of the methods, to regular project team meetings, providing a scientific steer and to the decision-making on the project. CF provided expert knowledge in regard to the New Zealand Mortality Collection. All authors contributed to the drafting and revision of the paper, and final approval, prior to submission. The funder had no involvement in any of the above.

  • Funding This research was supported by the New Zealand Accident Compensation Corporation (ACC).

  • Disclaimer The views expressed in this paper are those of the authors and do not necessarily reflect those of the ACC.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.