Injury in Australia

Injury case identification

A diagnosis of injury is defined as ICD-10-AM codes in the range S00–T75 or T79, using ‘Chapter 19 Injury, poisoning and certain other consequences of external causes’. A primary diagnosis of injury is when one of the specified codes is the first diagnosis code reported, while an additional diagnosis of injury is when one of the specified codes is reported but not as the first diagnosis.

A person may have more than one incident of injury resulting in hospitalisation in a financial year and each case of hospitalisation will be counted separately in this report. This is because we are counting incidents of injury resulting in hospitalisation, rather than the number of people who were hospitalised, in a given financial year. If a single incident led to an admission in more than one hospital, the incident has only been counted once. Therefore, counts of injury cases will be lower than the count of hospital records indicating injuries.

Inclusion criteria

• Records with the maximal snapshot id in any database where the date of separation falls within the timeframe defined in the report. 
• NHMD records with a principal diagnosis in the ICD‑10‑AM range S00–T75 or T79, using Chapter 19 Injury, poisoning and certain other consequences of external causes.
• NHMD records with a separation date between 1 July 2022 and 30 June 2023

Exclusion criteria

• Records were excluded where the AIHW ‘standard analysis’ flag was absent, i.e. care type was newborn with unqualified days only (7.3), organ procurement - posthumous (9), or hospital boarder (10).
• Injuries due to Complications of surgical and medical care (T80 – T88) and Sequelae of injuries, of poisoning and of other consequences of external causes (T90 – T98) are excluded.

Estimating index cases, not counting separations

Each record in the NHMD refers to a single episode of care in a hospital. Some injury incidents result in more than one episode of care and, therefore, more than one record. 

To minimise the impact of overcounting where a person experienced multiple episodes of care relating to the same condition, the following criteria are applied to estimate incidents:

• Excludes records where admission mode is transfer from another hospital (1)
• Excludes records where admission mode is statistical admission (2) and care type is not acute (1, 7.1, 7.2)
• Excluding records where care involving use of rehabilitation procedures (Z50) appears as an additional diagnosis and care type is not acute (1, 7.1, 7.2)

Injury classifications from ICD-10-AM

Diagnosis, intervention, activity, place of occurrence and external cause data for 2022–23 were reported to the NHMD using classifications from the 12th edition of the International statistical classification of diseases and related health problems, 10th revision, Australian modification (ICD-10-AM) (IHPA 2022), incorporating the Australian classification of health interventions (ACHI).

In tables and figures, information on diagnoses, external causes, activity, place of occurrence and interventions are presented using the codes and abbreviated descriptions of the ICD-10-AM/ACHI. Full descriptions of the categories are available in ICD-10-AM/ACHI publications on the Independent Health and Aged Care Pricing Authority (IHACPA) website (IHPA 2022).

Where data are presented in a time series incorporating previous reporting periods, these have been coded according to the following editions of ICD‑10‑AM:

• 7th edition for 2011–12 and 2012–13 hospital data
• 8th edition for 2013–14 and 2014–15 hospital data
• 9th edition for 2015–16 and 2016–17 hospital data
• 10th edition for 2017–18 and 2018–19 hospital data
• 11th edition for 2019–20, 2020-21, 2021–22 hospital data
• 12th edition for 2022–23 hospital data

Categorising external causes of injury

The NHMD is structured so that the first listed external cause for a record relates to the first listed injury diagnosis (principal diagnosis). While multiple external causes may be recorded for a separation, we report only one cause for each injury, referred to as ‘nominal external cause’ in these notes. The following steps are followed to determine the nominal external cause for each injury hospitalisation:

1. The first reported external cause is taken to be the nominal external cause
2. If the nominal external cause, as determined by step 1, is U90.0 (Healthcare associated Staphylococcus aureus bacteraemia) or a supplementary factor (Y90–Y98), then the second reported code is taken to be the nominal external cause
3. If the nominal external cause, after steps 1 and 2, relates to complications of medical and surgical care (Y40–Y84), sequelae of external causes of morbidity and mortality (Y85–Y89), or a supplementary factor code (Y90–Y98), then the record is excluded.

The categorisation of external causes using ICD-10-AM codes are detailed in Appendix tables to technical notes for Injury in Australia [XLSX 150kB].

Categorising type, body part, activity and place of injury

Type of injury and body part injured are based on the patient’s principal diagnosis. Principal diagnosis is the diagnosis chiefly responsible for occasioning the episode of care for the patient as defined by ICD-10-AM codes. The principal diagnosis details the type of injury sustained such as fractures, dislocations, nerve injuries and burns, and the body part injured such as head, neck, ankle and foot.

To categorise injuries by type and body part injured, Injury in Australia’s principal diagnosis matrix has been applied (as outlined in the Appendix tables to technical notes for Injury in Australia [XLSX 150kB]).

The sum of injuries by body part may not equal the total number of hospitalised injury cases because some injuries are not described in terms of body region.

Activity while injured and place of occurrence of injury are reported as recorded from external cause of injury data. Where appropriate these may be clustered into like categories and presented as such.

Analysis methods

The Australian ERP as at 30 June 2001 is used as the standardising population throughout the report. Age‑standardisation of rates enables valid comparison across years and/or jurisdictions without being affected by differences in age distributions.

Population‑based rates of injury tend to have similar values from one year to the next. Exceptions to this can occur (for example, due to a mass‑casualty disaster), but are unusual in Australian injury data. Some year‑on‑year variation and short‑run fluctuations are to be expected, so small changes in a rate over a short period do not provide a firm basis for asserting that a trend is present.

n.a. Not Applicable

Note that ‘average length of stay’, as presented in this report, does not include some patient days potentially attributable to injury. It does not include days for most aspects of injury rehabilitation, which cannot be reliably assigned without information enabling identification of all admitted episodes associated with an injury case.

Timeseries

10-year time series rates may not match historically published rates due to changes in denominator data over time, jurisdictional updates in numerator data or retrospective refreshing of numerator or denominator data across different data sources.

Presentation of data

Persons totals include cases for which sex was not reported.

All age totals include cases where age was not reported.

Percentages, rates (crude/age-specific and age-standardised), and average length of stay (ALOS) figures are rounded to 1 decimal place. Percentages may not add up to 100.0 because of rounding. Both crude/age-specific rates and age-standardised rates are calculated per 100,000 population.

Data suppression and confidentiality

Aggregated injury hospitalisations data are usually presented in tables, graphs, or maps. To avoid attribute disclosure and minimise risk of potentially re-identifying a person, data suppression rules have been applied.

Consequential suppression may also be applied to prevent a suppressed cell from being calculated. This is often done by suppressing table cells in the same row or column or suppressing the table totals.

Counts

• Counts less than 5 are suppressed and consequential suppression is applied.
• When data are disaggregated by geography location, counts for areas where the population is less than 1,000 are suppressed.

Crude rates

• Crude rates with counts (numerator for calculation) less than 10 are suppressed.
• If the corresponding counts measure is suppressed, the crude rate has been suppressed.
• When data are disaggregated by geography location, counts for areas where the population is less than 100 are suppressed.

Age-standardised rates

• Age-standardised rates with counts (numerator for calculation) less than 20 are suppressed.
• If the corresponding counts measure is suppressed, the age-standardised rate has been suppressed.
• When data are disaggregated by geography location, counts for areas where the population is less than 30 are suppressed.

Z-score

No suppression applied.

Data quality

A summary of data notes and data quality issues for the NHMD can be found in the Admitted Patient Care technical notes and appendices on MyHospitals. Additionally, please refer to the interactive timeline in Figure 1 of these technical notes for key data quality related changes over time.

The key issues are:

First Nations status

The AIHW report Indigenous identification in hospital separations data: quality report (AIHW 2013) presents findings on the quality of First Nations identification in hospital separations data in Australia, based on studies conducted in public hospitals during 2011. Private hospitals were not included in the assessment. The findings indicate that, overall, the quality of First Nations identification in hospital separations data was similar to that achieved in a previous study (AIHW 2010). However, the survey for the 2013 report was performed on larger samples for each jurisdiction/region and is therefore considered more robust than the previous study. An estimated 88% of First Nations patients were correctly identified in Australian public hospital admission records in 2011–12 (AIHW 2013). This under counting of First Nations patients is a known issue across states and territories with proportions ranging from 58% (confidence interval, 46-69%) in the Australian Capital Territory to 98% (96-99%) in the Northern Territory over the same time period.

Variation in state and territory coding practices

The emergency department admission policy was changed for New South Wales (NSW) hospitals in 2017–18. Episodes of care delivered entirely within a designated emergency department or urgent care centre are no longer categorised as an admission regardless of the amount of time spent in the hospital. This narrowing of the categorisation has had the effect of reducing the number of admissions recorded in NSW from the 2017–18 financial year. For NSW, the effect was a significant decrease (3.7%) in all public hospital admissions in 2017–18 compared to 2016–17. The impact of the change was felt disproportionately among hospitalisations for injury and poisoning. According to NSW Health, the number of hospitalisations for injury and poisoning in NSW decreased by 7.6% between 2016–17 and 2017–18, compared to a usual yearly increase of 2.8% (Centre for Epidemiology and Evidence 2019).

The change in NSW’s emergency department admission policy may have had different effects on case numbers within different external cause categories. This is because different types of injury have a different likelihood of requiring prolonged care in an emergency department, but without an admission to a hospital ward.

Due to the size of the contribution of NSW data to the national total, Australian data from 2017–18 should therefore not be compared with data from previous years.

Cross-border flow of patients

Data on state or territory of hospitalisation should be interpreted with caution because of cross-border flows of patients. This is particularly the case for the Australian Capital Territory. In 2022–23, 17% of separations for Australian Capital Territory hospitals were for patients who lived in New South Wales.