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Studies need to make explicit the theoretical and case definitions of injury
  1. Colin Cryer,
  2. John D Langley
  1. Injury Prevention Research Unit, University of Otago, Dunedin, New Zealand
  1. Dr C Cryer, Associate Professor, Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, New Zealand; colin.cryer{at}

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Pick up almost any issue of Injury Prevention and you will find statements such as the following:

“Results of this study are subject to limitations. NEISS-AIP only includes injuries treated in hospital emergency departments and thus excludes those treated in physician offices, outpatient clinics or at home. Our results then are probably an undercount of the total injuries sustained.”1

This statement is meaningless unless the authors say what they are talking about: what injuries they are seeking to describe. An essential element of the description of the study methods, for papers that deal with quantitative results, is a clear statement of the definition of injury that is the intended focus of the paper.

In the above example, if the authors were interested in describing all injuries, including trivial or superficial injuries, then they had no business using attendance at the emergency department (ED) as their case definition, as it is patently clear that ED data would capture only a minority of these trivial injuries. One reason for using ED data to describe the epidemiology of injury is that no-one is interested in preventing trivial injuries. Rather we are interested in preventing injuries that are consequential, eg, in terms of death, threat to life, (threat of) disability, reduced quality of life, and cost.

This quote typifies what we have read in many injury epidemiology papers. Many of these papers use case definitions of convenience (eg, ambulance attendances, ED attendances, hospitalizations) to describe the epidemiology of injury without any definition of the underlying injury outcome of interest. As we will demonstrate, this is “putting the cart before the horse”. We contend that, in order for the reader of a paper to assess whether the chosen case definition used is appropriate, he/she needs to know what injuries are the focus of the …

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  • Competing interests: None.