Appendix B: Technical notes


If not otherwise indicated, data elements were defined according to the definitions in the Local Hospital Networks/Public hospital establishments NMDS 2017–18 are also available online in the AIHW metadata online registry, METeOR. These are summarised in the Glossary.

Geographical classification

Information on the location of public hospitals is reported to the NPHED. The remoteness area of each public hospital was determined based on its street address.

Data on geographical location of the hospital location are defined using the ABS’s Australian Statistical Geography Standard (ASGS) Remoteness Structure 2016  which categorises geographical areas in Australia into remoteness areas. The classification is as follows:

  • Major cities—for example: Sydney, Melbourne, Brisbane, Adelaide and Perth
  • Inner regional—for example: Hobart, Launceston, Wagga Wagga and Bendigo
  • Outer regional—for example: Darwin, Moree, Cairns, Charters Towers and Albany
  • Remote—for example: Port Lincoln, Esperance, Queenstown and Alice Springs
  • Very remote—for example: Mount Isa, Coober Pedy, Port Hedland and Tennant Creek.

Australian Refined Diagnosis Related Groups

In this report, Australian Refined Diagnosis Related Groups (AR-DRG) sourced from the National Hospital Morbidity Database (NHMD) are used to measure the complexity of cases in hospitals (for example, counts of AR-DRGs for which a hospital reported at least 5 separations) and to derive the clinical specialties that are provided by hospitals (for example, using Service Related Groups).

For more information on the AR-DRG classification, see Admitted patient care 2017–18: Australian hospital statistics.

Presentation of data

Throughout the publication, percentages may not add up to 100.0 because of rounding. Percentages and rates printed as 0.0 or 0 generally indicate a zero. The symbol ‘<0.1’ has been used to denote less than 0.05 but greater than 0.

Suppression of data

The AIHW operates under a strict privacy regime which has its basis in Section 29 of the Australian Institute of Health and Welfare Act 1987 (AIHW Act). Section 29 requires that confidentiality of data relating to persons (living and deceased) and organisations be maintained. The Privacy Act 1988 governs confidentiality of information about living individuals.

The AIHW is committed to reporting that maximises the value of information released for users while being statistically reliable and meeting legislative requirements described above.

Data (cells) in tables may be suppressed in order to maintain the privacy or confidentiality of a person or organisation, or because a proportion or other measure related to a small number of events and may therefore not be reliable.

Analysis methods

Counting activity

Counts of separations and patient days were sourced from admitted patient care data reported for the NHMD for 2017–18.

Records for 2017–18 are for hospital separations in the period from 1 July 2017 to 30 June 2018. Data on patients who were admitted on any date before 1 July 2017 are included, provided that they also separated between 1 July 2017 and 30 June 2018. A record is included for each separation, not for each patient, so patients who separated more than once in the year have more than one record in the NHMD.

Records for Newborn episodes without qualified days and records for Hospital boarders and Posthumous organ procurement were excluded from counts of separations. However, for analyses based on SRGs, Newborn episodes without qualified days were also included.

A patient day (or day of patient care) means an admitted patient occupied a hospital bed (or chair in the case of some same-day patients) for all or part of a day. The length of stay for an overnight patient is calculated by subtracting the date the patient is admitted from the date of separation and deducting days the patient was on leave. A same-day patient is allocated a length of stay of 1 day.

Patient day statistics can be used to provide information on hospital activity that, unlike separation statistics, account for differences in length of stay. As the database contains records for patients separating from hospital during the reporting period (1 July 2017 to 30 June 2018), this means that not all patient days reported will have occurred in that year.

It is expected, however, that patient days for patients who separated in 2017–18, but who were admitted before 1 July 2017, will be counterbalanced overall by the patient days for patients in hospital on 30 June 2018 who will separate in future reporting periods.

Estimated resident populations

All populations are based on the estimated resident population as at 30 June preceding the reporting period (that is, for the reporting period 2017–18, the estimated resident population as at 30 June 2017 was used), drawn from the 2016 Census data.

Hospital peer groups

This report uses the AIHW current peer group classification, developed by the AIHW in consultation with the Australian Hospital Statistics Advisory Committee and the Private Hospital Statistics Advisory Committee in 2013 and 2014. Peer group classifications are outlined in the 2015 report Australian hospital peer groups.

The peer group to which each public hospital is assigned is included in Table AS.1 available to download in the Data section of this report.