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Severity of injury measures and descriptive epidemiology
  1. C Cryer
  1. Correspondence to:
 Colin Cryer
 Injury Prevention Research Unit, Department of Preventive and Social Medicine, University of Otago, P O Box 913, Dunedin, New Zealand; colin.cryer{at}

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The ICISS method for deriving severity of injury is available to all and, until shown otherwise, it is the threat-to-life severity measure of choice for the ICD-10 era

In those countries with national hospital inpatient data systems, we want to use these admissions/discharges/separations (henceforth, referred to as admissions) data for a variety of purposes. At the population level, these include for describing the epidemiology of injury, developing injury indicators, and injury surveillance. In this editorial, I will concern myself solely with the use of these data for descriptive epidemiological purposes.

We know that health service use, following injury, including admission to hospital, is influenced by many factors that are independent of the severity of the injury, including bed availability, access (for example, distance from home to hospital/rurality), concern about intentionality (for example child abuse), and professional variations in practice.1 So, in a descriptive epidemiological analysis, using admission to hospital as the definition of a case of injury is likely to give a biased picture of the variations in injury incidence by person, place, or time, as well as by external cause.

Defining cases of injury according to whether the injury exceeds a given severity threshold, with the threshold chosen to ensure nearly complete ascertainment from the data source, is one way to overcome these problems.2 This begs the question: how should severity be measured when using admissions data?


Severity can be measured on a number of dimensions. Historically the focus in the literature has been on measures of severity in terms of damage to the body that have been validated against mortality outcomes. These are referred to as threat-to-life severity measures. Little attention has been given to another equally important dimension, namely threat-of-disability. This dimension is also important, and threat-to-life measures are poor predictors of disability. Nevertheless, I …

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  • See linked article on p 111

  • Competing interests: none.

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