Technical notes
Data sources
Hospitalisations data are sourced from the Australian Institute of Health and Welfare’s (AIHW) National Hospital Morbidity Database (NHMD). The NHMD is a compilation of episode-level records from admitted patient morbidity data collection systems (APC NMDS) in Australian public and private hospitals. It includes episodes of care for admitted patients in all public and private acute and psychiatric hospitals, free standing day hospital facilities and alcohol and drug treatment centres in Australia. Hospitals operated by the Australian Defence Force, corrections authorities and in Australia's offshore territories may also be included. Hospitals specialising in dental, ophthalmic aids and other specialised acute medical or surgical care are included. Data quality statements for the NHMD are available on the AIHW MyHospitals website. For more information about data contained in the NHMD refer to the AIHW MyHospitals technical notes.
Emergency department data are sourced from the National Non-admitted Patient Emergency Department Care Database (NNAPEDCD). Data quality statements for this dataset are available on the AIHW MyHospitals website. For the 2021–22 NAPEDC NMDS/NBEDS, diagnosis information was reported using the ED ICD-10-AM version 11 shortlist that can be found on the website of the Independent Hospital Pricing Authority.
For more information about data contained in the NNAPEDCD refer to the MyHospitals technical notes for recent years.
Population data are used for demographic analyses and as the denominator in calculating rates. All population level calculations are based on the estimated resident population (ERP) calculated as at the midpoint of each financial year. For example, for the reporting period 2021–22, the denominator population is the June 2021 ERP + the June 2022 ERP, divided by 2. This is used as the denominator for age‑specific/crude and age‑standardised rates.
The ERP as at 30 June 2001 is used as the standardising population throughout the report (ABS 2003).
All population data are sourced from the Australian Bureau of Statistics (ABS) as follows:
- General populations are from National, state and territory population (Australian Bureau of Statistics 2023, March)
- Remoteness populations (available on request from ABS)
- Socio-Economic Indexes For Areas (SEIFA) Index of Relative Socio-Economic Disadvantage (IRSD) quintile populations are from AIHW analysis of Census of Population and Housing: Socio-Economic Indexes for Areas (ABS 2018) and Regional Population by age and sex (Australian Bureau of Statistics 2022).
What is counted in this report?
Cases of injury are included in numerators or counts in this report where injury case identification criteria are fulfilled and an external cause of contact with animals can be ascertained.
The 2021-22 financial year except for trends over time, which are described by financial year between 2012-13 and 2021-22.
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 2012 to 30 June 2022
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)
Diagnosis, intervention, and external cause data in the NHMD for 2021–22 was reported to using classifications from the 11th edition of the International statistical classification of diseases and related health problems, 10th revision, Australian modification (ICD-10-AM) (ACCD 2019a).
In tables and figures, information on diagnoses, external causes, and interventions are presented using the codes and abbreviated descriptions of the ICD-10-AM and the 11th edition of the Australian classification of health interventions (ACHI). Full descriptions of the categories are available in ICD-10-AM/ACHI publications (ACCD 2019a, ACCD 2019b, ACCD 2019c).
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 and 2021–22 hospital data
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:
- The first reported external cause is taken to be the nominal external cause
- If the nominal external cause, as determined by step 1, is U90.0 (Staphylococcus aureus) or a supplementary factor (Y90–Y98), then the second reported code is taken to be the nominal external cause
- 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.
ICD10-AM codes indicating where a nominal external cause of injury is due to contact with animals are listed in Table 13.
W53 Bitten by rat | W55 Bitten or struck by other mammals | W57 Bitten or stung by nonvenomous insect and other nonvenomous arthropods |
W54 Bitten or struck by dog | W56 Contact with marine animal | W58 Bitten or struck by crocodile or alligator |
W59 Bitten or crushed by other reptiles | W61 Contact with bird | X20–25, X27 Contact with venomous animals |
Y37.6 Allergy to animals | X26.0 Contact with Jellyfish | X26.1 Contact with stinging fish |
X26.2 Contact with venomous octopus | X26.3 Contact with stingray | V80.00-V80.99 Animal-rider or occupant of animal-drawn vehicle injured in transport accident |
ICD10-AM codes where the external cause may include, but is not specifically limited to, contact with an animal are included in Table 11. These cases are excluded from the main body of analysis. Injury in Australia includes these in counts of ‘Contact with living things'.
X26.8 Contact with other specified venomous marine animals and plants | X29 Contact with unspecified venomous animal or plant | W64 Exposure to other and unspecified animate mechanical forces |
ICD10-AM codes where the external cause of injury is transport related and may involve an animal are outlined in Table 12. In these cases, injuries are sustained during collision with pedestrians or animals. Injuries sustained in collisions with animal-drawn vehicles are excluded as we are unable to ascertain from ICD10-AM codes whether the animal or the vehicle was involved in the collision. These cases are excluded from the main body of analysis.
V20 Motorcycle rider injured in collision with pedestrian or animal | V30 Occupant of three-wheeled motor vehicle injured in collision with pedestrian or animal | V40 Car occupant injured in collision with pedestrian or animal |
V50 Occupant of pick-up truck or van injured in collision with pedestrian or animal | V60 Occupant of heavy transport vehicle injured in collision with pedestrian or animal | V70 Bus occupant injured in collision with pedestrian or animal |
Definitions
If not otherwise indicated, data elements were defined according to their definitions in the AIHW’s Metadata Online Registry (METEOR) and summarised in the Glossary.
Data element definitions for the NHMD and NNAPEDCD are available online on the METEOR website.
The terms ‘injury hospitalisation’, ‘hospitalised injury’ and ‘hospitalised case’ in this report refer to incidents where a person was admitted to hospital with injury as the main reason. If a single incident led to an admission in more than one hospital, the incident has only been counted once.
Categories in Table 16 and Table 17 are not mutually exclusive.
Category | ICD10-AM codes |
|---|---|
Common pets | W54.0 Bitten by dog W54.8 Other contact with dog: Struck by dog W55.1 Bitten or struck by cat: Scratched by cat Y37.63 Allergy to cats Y37.64 Allergy to dogs |
Livestock | W55.0 Bitten or struck by horse W55.2 Bitten or struck by cattle, including where bitten or struck by:
W55.3 Bitten or struck by sheep |
Wildlife (excluding marine animals) | W57 Bitten or stung by nonvenomous insect and other nonvenomous arthropods W58 Bitten or struck by crocodile or alligator W59.0 Bitten or crushed by nonvenomous snake W59.1 Bitten or crushed by snake, unknown whether venomous or nonvenomous, Bitten or crushed by snake NOS W59.8 Bitten or crushed by other specified reptile, Bitten or crushed by nonvenomous lizard W61.0 Contact with magpie X20 Contact with venomous snakes and lizards X21 Contact with spiders X22 Contact with scorpions X23 Contact with hornets, wasps and bees X24 Contact with centipedes and venomous millipedes (tropical) X25 Contact with other venomous arthropods X27.0 Contact with platypus Y37.61 Allergy to bees Y37.62 Allergy to birds |
Marine animals | W56.0 Contact with shark W56.8 Contact with other specified marine animal W56.9 Contact with unspecified marine animal X20.05 Contact with sea-snake X26.0 Contact with jellyfish X26.1 Contact with stinging fish X26.2 Contact with venomous octopus X26.3 Contact with stingray |
Other and unspecified | W53 Bitten by rat W55.8 Bitten or struck by other specified mammal W55.9 Bitten or struck by unspecified mammal W61.8 Contact with other specified bird W61.9 Contact with unspecified bird X27.8 Contact with other and unspecified venomous animals Y37.60 Allergy to animal, unspecified Y37.69 Allergy to other animal V80.00-V80.99 Animal-rider or occupant of animal-drawn vehicle injured in transport accident |
Animals have been categorised in Table 17 where codes specifically identify their venomous status. Codes including unspecified animals are excluded from this categorisation. Summing venomous and non-venomous categories will therefore not equal total contact with animals counts.
Venomous animals | X20 Contact with venomous snakes and lizards. Includes brown snakes (X20.00), taipans (X20.01), death adders (X20.02), black snakes (X20.03), tiger snakes (X20.04), sea-snakes(X20.05), other or unspecified snakes (X20.08 & X20.09) and venomous lizards (X20.1) X21 Contact with spiders. Includes funnel webs (X21.0), red backs (X21.1), necrotising spiders including white-tails (X21.2), other specified or unspecified spiders (X21.8 & X21.9). X22 Contact with scorpions X23 Contact with hornets, wasps and bees. X24 Contact with centipedes and venomous millipedes (tropical) X25 Contact with other venomous arthropods. Includes venomous ants (X25.0), ticks (X25.1), caterpillars (X25.2) other and unspecified arthropods (X25.8 & X25.9) X26.0 Contact with jellyfish. Includes box (X26.00), Irukandji (X26.01), bluebottles (X26.02), other specified and unspecified jellyfish (X26.08 & X26.09) X26.1 Contact with stinging fish X26.2 Contact with venomous octopus X26.3 Contact with stingray X27.0 Contact with platypus X27.8 Contact with other and unspecified venomous animals Y37.61 Allergy to bees |
|---|---|
Non-venomous animals | W53 Bitten by rat W54.0 Bitten by dog W54.8 Other contact with dog: Struck by dog W55.0 Bitten or struck by horse W55.1 Bitten or struck by cat: Scratched by cat W55.2 Bitten or struck by cattle W55.3 Bitten or struck by sheep W55.8 Bitten or struck by other specified mammal W56.0 Contact with shark W56.8 Contact with other specified marine animal W56.9 Contact with unspecified marine animal W57 Bitten or stung by nonvenomous insect and other nonvenomous arthropods W58 Bitten or struck by crocodile or alligator W59.0 Bitten or crushed by nonvenomous snake W59.8 Bitten or crushed by other specified reptile, Bitten or crushed by nonvenomous lizard W61.0 Contact with magpie W61.8 Contact with other specified bird Y37.62 Allergy to birds Y37.63 Allergy to cats Y37.64 Allergy to dogs |
There are a series of five monovalent antivenoms for use in the treatment of Australian land snake bites, a sea snake antivenom and various exotic antivenoms used to treat bites from non-Australian venomous snakes (e.g. kept in zoos). A polyvalent antivenom is also available combining all five monovalent antivenoms where the species of snake is not identified. Antivenoms are also available for stonefish, paralysis tick, red back spider and funnel web spider.
Patients may receive multiple ampoules of antivenom. Such patients may have these ampoules given as single boluses or the contents of two ampoules combined.
Administration of antivenom is assigned a code from block [1920] Administration of pharmacotherapy with an extension of -04. These include:
- 96196-04 Intra-arterial administration of pharmacological agent, antidote
- 96197-04 Intramuscular administration of pharmacological agent, antidote
- 96198-04 Intrathecal administration of pharmacological agent, antidote
- 96199-04 Intravenous administration of pharmacological agent, antidote
- 96200-04 Subcutaneous administration of pharmacological agent, antidote
- 96201-04 Intracavitary administration of pharmacological agent, antidote
- 96202-04 Enteral administration of pharmacological agent, antidote
- 96203-04 Oral administration of pharmacological agent, antidote
- 96205-04 Other administration of pharmacological agent, antidote
- 96206-04 Unspecified administration of pharmacological agent, antidote
- 96209-04 Loading of drug delivery device, antidote
Type of injury includes, for example, fractures and poisoning. Site of injury includes, for example, head and neck or wrist and hand.
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). Body part and injury type are derived from the principal diagnosis of the case. 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.
Characteristic | Notes |
|---|---|
Sex | The NHMD reports sex as male or female. Persons totals include records where sex is not defined and may therefore not equal male + female counts. |
Age and age-group | The patient’s age is calculated at the date of admission. In tables by age group and sex, separations for which age and/or sex were not reported are included in the totals. Age is presented categorised into life-stage age groups namely 0-4,5-14,15-24,25-44,45-64 and 65+ years. |
Remoteness | SA1 or SA2 area of usual residence as supplied in the NHMD is mapped to the ABS’s ASGS Remoteness structure 2016 [1] and categorised into the following remoteness regions; major cities, inner regional, outer regional, remote and very remote. Due to small counts, remote and very remote regions have been aggregated in this report to reduce the need for data suppression. |
Analysis
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.
All rate calculations utilise a denominator based on the estimated resident population (ERP) calculated as at the midpoint of each financial year. For example, for the reporting period 2021–22, the denominator population is the June 2021 ERP + the June 2022 ERP, divided by 2. This is used as the denominator for age‑specific/crude and age‑standardised rates. Rates are calculated for each financial year unless otherwise noted.
| Measure | Numerator | Denominator | Calculation |
|---|---|---|---|
Population (used for rates) | June 21 population + June 2022 population | 2 | Numerator ÷ Denominator |
Crude or age-specific rate of hospitalisation | Number of cases of injury hospitalisation per defined category (e.g. age group) | Estimated Australian population as at mid-point of financial year | (Numerator ÷ Denominator) x 100,000 |
Age-standardised rate (ASR). Age-standardised rates were derived using 5-year age groups up to 85+. Age-standardised rates for First Nation populations were derived using 5-year age groups up to 65+. | Expected events per age group in standard population= crude rate of hospitalisation x standard population (for each corresponding age group) |
| The direct method of standardisation is used. (Sum of numerators across all age groups ÷ total standard population) x 100,000 |
Average length of stay | Number of patient bed days | Number of cases | Numerator ÷ Denominator, as days, rounded to 1 decimal place |
Change in rates
|
|
| Estimated trends in age-standardised rates were reported as average annual percentage changes.
|
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.
Due to rounding, percentages in tables may not add up to 100.0.
Remoteness is based off the patient’s usual place of residence. Remoteness areas in Australia are comprised of 5 groups (Major Cities, Inner Regional, Outer Regional, Remote, and Very Remote) categorised by the Accessibility/Remoteness Index of Australia Plus (ARIA+). These ARIA+ values are derived using the Statistical Area Level 1 (SA1) from the Australian Statistical Geography Standard (ASGS) 2016.
| Remoteness area | Average ARIA+ range for SA1 |
|---|---|
Major Cities of Australia | 0 to 0.2 |
Inner Regional Australia | Greater than 0.2 and less than or equal to 2.4 |
Outer Regional Australia | Greater than 2.4 and less than or equal to 5.92 |
Remote Australia | Greater than 5.92 and less than or equal to 10.53 |
Very Remote Australia | Greater than 10.53 |
Counts are presented as whole numbers.
Crude/age-specific rates and age-standardised rates are calculated per 100,000 population and are rounded to 1 decimal place.
Proportions (%) and ALOS are also rounded to 1 decimal place.
Aggregated injury hospitalisations data are usually presented in tables, graphs, or maps. To maintain attribute disclosure and minimise risk of potentially re-identifying a person, data suppression rules have been applied.
Sometimes consequential suppression is also applied to prevent the primary 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 (hospitalisations)
- Counts less than 5 are suppressed and consequential suppression is applied unless that count applies to a whole of population level, in which case it may be published unsuppressed if there is not further ability to disaggregate by population groups.
- When data is 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 is disaggregated by geography location, counts for areas where the population is less than 1,000 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 is disaggregated by geography location, counts for areas where the population is less than 30 are suppressed.
Notes on data
- Over time, minor changes have been made to the method for counting cases of injury, therefore data presented in previous AIHW reports may not match the data presented in this report.
- Only a small proportion of all incidents of injury result in admission to a hospital. For each admission, many more people with injuries are treated in an emergency department but not admitted, or visit a general practitioner, physiotherapist or Urgent Care/Walk-in Clinic rather than a hospital. A larger number of minor injuries do not receive any medical treatment. A smaller number of severe injuries that quickly result in death do not include a stay in hospital but are captured in mortality data.
- This report only reflects injuries where external causes are coded and the injury is identifiable as due to contact with animals. It only counts injuries that present to Australian hospitals or EDs. This report therefore underestimates the total burden of injuries due to contact with animals as it does not count injuries where health care is not sought from a hospital or emergency department.
- Minor injuries (e.g. scratches and stings) are likely underrepresented in this report as injury hospitalisations or ED presentations are likely biased towards injuries perceived as severe enough to require health care intervention. By the same logic, injuries caused by venomous animals are likely to be over-represented in this report.
- ICD10-AM codes including injuries due to plants and animals or humans and animals are excluded from this report due to inability to ascertain what type of animate mechanical forces are involved.
- The NHMD does not provide unique identifiers and this report is unable to present information about the number of people injured. We instead present information about the number of cases of injury.
- The COVID-19 pandemic and the resulting Australian Government closure of the international border from 20 March 2020, caused significant disruptions to the usual Australian population trends. This report uses Australian Estimated Resident Population (ERP) estimates that reflect these disruptions.
In the year July 2020 to June 2021, the overall population growth was much smaller than the years prior and in particular, there was a relatively large decline in the population of Victoria. ABS reporting indicates these were primarily due to net-negative international migration (National, state and territory population, June 2021 | Australian Bureau of Statistics (abs.gov.au)).
Please be aware that this change in the usual population trends may complicate your interpretation of statistics calculated from these ERPs. For example, rates and proportions may be greater than in previous years due to decreases in the denominator (population size) of some sub-populations. - Overall, the quality of the data in the NNAPEDCD is sufficient to be published in this report. However, limitations of the data as listed in the NNAPEDCD technical notes should be taken into consideration when ED data are interpreted.
- The recording of external cause information is not as complete in the NNAPEDCD as the NHMD. A short list of ICD10 codes are used and the proportion of missing data is higher than the NHMD. This analysis quantifies the number of NNAPEDCD records in the latest financial year of the timeframe of interest, where the following can be ascertained:
- An injury diagnosis in any available primary or additional diagnosis variable AND
- An external cause code related to contact with animals in any primary or additional diagnosis variable
Where the sum of cases identified by the above two criteria constituted 5% or less of all ED records in the latest financial year of the timeframe of interest, ED data was not described further. This is due to unreliability of data for injury surveillance due to under-recording or unavailability of external cause related information in the ED dataset.
- The emergency department admission policy was changed for New South Wales (NSW) hospitals in 2017–18 and detailed in the NHMD technical notes. 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. Due to the size of the contribution of NSW data to the national total, there is a break in series in Australian data from before and after 2017–18.