Method: Injury and Poisoning
Records based on place of residence
Most of the analyses are based on the place of residence of the person, rather than the place they were treated, or, in the case of an injury, the place the injury occurred. It should be noted that the injury that led to a person's hospitalisation might not have occurred in the area in which the person resided. For example, metropolitan residents may be injured in motor vehicle crashes while travelling in regional or remote areas. The location where injury was sustained is not routinely recorded in hospitalisation statistics.
‘External cause’ as the basis for injury count
The International Statistical Classification of Diseases and Related Health Problems (ICD-10) (IHPA 2019) groups injury according to the body region which is affected by injury (head, neck chest etc) and the type of injury (superficial, fracture, amputation etc). Relevant codes are ICD-10: S00 to T98. Another way of categorising injury is by the circumstances of injury or the activity being undertaken when injured (transport accidents, assaults, intentional self-harm etc). This group is covered by ICD-10 codes U50-Y98 called ‘external causes’ (IHPA 2019).
In HealthStats NSW hospitalisations and deaths due to injury are classified by the external cause of injury. This is because this classification is the most important in prevention planning as it identifies factors that are amenable to intervention.
Rules for excluding records in analysis of hospitalisation for injury
In HealthStats NSW, injury hospitalisation data exclude records with source of referral being a transfer from another hospital or a type change admission in order to reduce multiple counting of hospitalisation episodes relating to the same injury incident. Some injury and poisoning hospitalisations require subsequent hospitalisations for rehabilitation. To avoid counting multiple hospitalisations following one injury event, rehabilitation is generally excluded.
Injury in primary diagnosis and external cause of injury
The majority of injury and poisoning hospitalisations have a principal diagnosis of injury and poisoning, but there is also a substantial number of hospitalisations where injury or poisoning is in an additional diagnosis (about 20%-30% of total records with injury and poisoning anywhere on record). Some of these hospitalisations are linked to a prior episode of hospitalisation with an injury in principal diagnosis, that has not been counted, due to the methods used to minimise multiple-counting of hospitalisations following one injury event, as explained in 'Rules for excluding records in analysis of hospitalisation for injury'.
Consequently, it is important to note whether an analysis included any hospitalisation records with external cause of injury or only those records that had injury and poisoning as the principal diagnosis.
Injury-related deaths
Injury deaths may be reported following a method which takes account of multiple causes of death (Henley G et al. 2007). The multiple causes of death method includes a death as an injury death if:
• the underlying cause of death was coded to ICD-10 V01–Y36, Y85–Y8, or Y89, or
• there is any cause of death coded to ICD-10 S00–T75 or T79 (AIHW Cat. no. AUS 122 2010) (see above for the categories of codes).
The resulting count was called injury-related deaths and was adopted in the Australia’s health 2010 report by the AIHW (AIHW Cat. no. AUS 122 2010).
The difference in count depending on the method applied could be as high as 25% in the same year (8,000 injury deaths in Australia in 2005 according to a straightforward method and 10,000 using the multiple causes of death).
In the HealthStats NSW injury and poisoning indicators a straightforward method of counting injury death has been used and the resulting count is based solely on the underlying cause of death coded to ICD-10 V01–Y36, Y85–Y87, or Y89 and the corresponding ICD-9 codes.
References
Australian Institute of Health and Welfare. Australia’s health 2010. Australia’s health series no. 12. Cat. no. AUS 122. Canberra: AIHW, 2010. Available at http://www.aihw.gov.au/publication-detail/?id=6442468376
Henley G, Kreisfeld R, Harrison J. Injury deaths, Australia
2003-04. Injury research and statistics series no. 31. AIHW cat. no.
INJCAT 89. Adelaide: AIHW, 2007. Available at
https://www.aihw.gov.au/getmedia/2daac948-ec7f-4a7d-bc22-889f5a54c8ab/injcat89.pdf.aspx?inline=true
Independant Hospital Pricing Authority (IHPA) The International statistical classification of diseases and related health problems, 11th Revision, Australian Modification (ICD-10-AM). Australian Coding Standards. Sydney, 2019.