Injury outcome indicators--validation matters

There is concern that many national non-fatal injury indicators currently in use are misleading.

To make the case for the validation of existing unvalidated indicators, as well as the validation of new indicators before they are promulgated.

The International Collaborative Effort on Injury Statistics (ICE) Criteria were used for investigating the validity of indicators. Examples of indicators that have been found to be valid using these criteria are presented. In contrast, examples of national road safety indicators are also presented, whose validity is questionable. Trends in road safety indicators with and without threats to validity are contrasted.

The New Zealand Injury Prevention Strategy (NZIPS) serious injury indicators are presented as indicators with no identifiable threats to validity. National road safety indicators from Canada, New Zealand and the United Kingdom, with identifiable threats to validity, are also presented. When trends for the valid NZIPS motor vehicle traffic crash indicators are compared with the New Zealand national road safety indicators, which have identifiable threats to validity, they show contrasting trends. This raises concerns that the current national indicators are potentially misleading.

Validation does matter. For any indicator, it is important that it is clearly defined and specified. The specification should make it clear what parameter the indicator aims to reflect. Before use, the indicator should be validated against this target parameter. That parameter, and the indicators aimed to estimate it, should focus attention on important injuries, ie. injuries that are associated with significant mortality, threat-to-life, threat-of-disablement, loss of quality of life, or increased cost.