The definition of opioid-related deaths in Australia: implications for surveillance and policy.

The reported number of deaths caused by opioid use depends on the definition of an opioid-related death. In this study, we used Australian Bureau of Statistics (ABS) mortality data to illustrate how choice of classification codes used to record cause of death can impact on the statistics reported for national surveillance of opioid deaths. Using International Classification of Diseases version 10 (ICD-10) codes from ABS mortality data 1997-2002, we examined all deaths where opioids were reported as a contributing or underlying cause. For the 6-year period there was a total of 5,839 deaths where opioids were reported. Three possible surveillance definitions of accidental opioid-related deaths were examined, and compared to the total number of deaths where opioids were reported for each year. Age restrictions, often placed on surveillance definitions, were also examined. As expected, the number of deaths was higher with the more inclusive definitions. Trends in deaths were found to be similar regardless of the definition used; however, a comparison between Australian states revealed up to a twofold difference in the absolute numbers of accidental opioid-related deaths, depending on the definition. Any interpretation of reported numbers of opioid deaths should specify any restrictions placed on the data, and describe the implications of definitions used.