Technical notes

Detailed information on data sources and methods are in Section 1.2 and the Appendix of the companion PDF report.

Data for this report were sourced from the AIHW National Hospital Morbidity Database for the years 2012–13 to 2017–18. The data are based on the patient’s usual residence, not the location of the hospital. The data are based on the count of hospitalisations – repeat admissions by the same person are counted as separate hospitalisations, as are transfers of a person from one hospital to another. Therefore, PPH counts cannot be used to estimate the number of individuals with a particular condition.

Comparability of data

The most recent geography boundaries, remoteness classifications and PPH codes were used for all six years of data. For this reason, numbers in this report may differ slightly from those in previous PPH reports.

Trends in PPH over time can be affected by changes to codes and coding standards. The major changes affecting the interpretation of data in this report are outlined below.

Changed coding standard for ‘past history’ of viral hepatitis on 1 July 2013

Z22.51 Carrier of viral hepatitis B and Z22.59 Carrier of other specified viral hepatitis codes were reassigned as B18.0 Chronic viral hepatitis B with delta agent and B18.1 Chronic viral hepatitis B without delta agent. This increased the number of PPH for Other vaccine-preventable conditions, as discussed in Section 2.1 of the companion PDF report.

New reporting of principal diagnoses for rehabilitation care hospitalisations

A change to the coding standard was made from 1 July 2015 to record the underlying condition requiring rehabilitation as the principal diagnosis, rather than the code Z50.- Care involving the use of rehabilitation procedures.

The impact on PPH was relatively small. Rehabilitation admissions accounted for 2.2% to 2.3% of total PPH admissions between 2015–16 and 2017–18, as discussed in the Appendix of the companion PDF report.

Analysis of sociodemographic factors

In this report, “Indigenous Australians” include people identified as Aboriginal and/or Torres Strait Islander; “other Australians” include non-Indigenous Australians and people whose identity was not stated or not known.

Area of remoteness is based on the Australian Bureau of Statistics (ABS) Australian Statistical Geography Standard Remoteness Structure, 2016.

Socioeconomic areas are based on the ABS Index of Relative Socio-economic Disadvantage (IRSD). The five groups represent area-based socioeconomic disadvantage, from the least disadvantaged 20% of areas to the most disadvantaged 20%. Data from 2012–13 were calculated using 2011 IRSD scores; data from 2017–18 were calculated using 2016 IRSD scores.

Where appropriate, directly age-standardised rates were calculated using the 2001 Australian standard population.

Comparability between states and territories

States and territories vary in their policies for considering same day procedures as inpatient admissions or outpatient procedures (for example, intravenous iron infusions – see Section 2.3 of the report). Therefore, the rate of same day PPH may be underestimated nationally, and may not be comparable between jurisdictions.

Some states and territories contain a substantially higher proportion of remote areas than others, and the challenges of providing health care in these settings should be considered when interpreting variation in PPH rates between jurisdictions. Similarly, it should be borne in mind that although a relatively high proportion of people living in Very remote areas (47%) and the Northern Territory (30%) are Indigenous Australians, 61% of Indigenous Australians live in Major cities and Inner regional areas.