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Data Collection Overview

National Hospital Morbidity Database (NHMD)

Data Collection Sources

The National Hospital Morbidity Database (NHMD) is a compilation of episode-level records from admitted patient morbidity data collection systems in Australian hospitals. It is a comprehensive dataset that has records for all episodes of admitted patient care from essentially all public and private hospitals in Australia.
The data supplied are based on the National Minimum Data Set (NMDS) for Admitted patient care and include demographic, administrative and length of stay data, as well as data on the diagnoses of the patients, the procedures they underwent in hospital and external causes of injury and poisoning.
In 2011–12, diagnoses and external causes of injury and poisoning were recorded using the seventh edition of the International statistical classification of diseases and related health problems, 10th revision, Australian Modification (ICD-10-AM). Procedures were recorded using the seventh edition of the Australian Classification of Health Interventions (ACHI).

Institutional environments

The Australian Institute of Health and Welfare (AIHW) is a major national agency set up by the Australian Government under the Australian Institute of Health and Welfare Act 1987 to provide reliable, regular and relevant information and statistics on Australia’s health and welfare. It is an independent statutory authority established in 1987, governed by a management board, and accountable to the Australian Parliament through the Health portfolio.
The AIHW aims to improve the health and wellbeing of Australians through better health and welfare information and statistics. It collects and reports information on a wide range of topics and issues, ranging from health and welfare expenditure, hospitals, disease and injury, and mental health, to ageing, homelessness, disability and child protection.
The Institute also plays a role in developing and maintaining national metadata standards. This work contributes to improving the quality and consistency of national health and welfare statistics. The Institute works closely with governments and non-government organisations to achieve greater adherence to these standards in administrative data collections to promote national consistency and comparability of data and reporting.
One of the main functions of the AIHW is to work with the states and territories to improve the quality of administrative data and, where possible, to compile national datasets based on data from each jurisdiction, to analyse these datasets and disseminate information and statistics.
The Australian Institute of Health and Welfare Act 1987, in conjunction with compliance to the Privacy Act 1988, (Commonwealth) ensures that the data collections managed by the AIHW are kept securely and under the strictest conditions with respect to privacy and confidentiality.
For further information see the AIHW website
Data for the NHMD were supplied to the AIHW by state and territory health authorities under the terms of the National Health Information Agreement
The state and territory health authorities received these data from public and private hospitals. States and territories use these data for service planning, monitoring and internal and public reporting. Hospitals may be required to provide data to states and territories through a variety of administrative arrangements, contractual requirements or legislation.

Relevance and Scope

The purpose of the NHMD is to collect information about care provided to admitted patients in Australian hospitals. The scope of the NHMD is 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 off-shore territories are not in scope, but some are included.
The hospital separations data do not include episodes of non-admitted patient care provided in outpatient clinics or emergency departments. Patients in these settings may be admitted subsequently, with the care provided to them as admitted patients being included in the NHMD.
The NHMD is the source of information for three performance indicators for the National Healthcare Agreement and other national performance reporting.
Although the NHMD is a valuable source of information on admitted patient care, the data have limitations. For example, variations in admission practices and policies lead to variation among providers in the number of admissions for some conditions and procedures (such as chemotherapy and endoscopies).


The reference period for this data set is 2014–15. This includes records for admitted patient separations between 1 July 2014 and 30 June 2015.
The agreed date for supply of a first version of data (based on best efforts) was 30 October 2015. Six states and territories provided a first version of 2014–15 data to the AIHW at the end of October 2015 and all had provided their first version by 10 November 2016. A second version of the data was agreed to be supplied by 16 December 2015. All states and territories had provided the second version of the data by 23 December 2015. The data were published on 16 March 2016.


States and territories are primarily responsible for the quality of the data they provide. However, the AIHW undertakes extensive validations on receipt of data. Data are checked for valid values, logical consistency and historical consistency. Where possible, data in individual data sets are checked with data from other data sets. Potential errors are queried with jurisdictions, and corrections and resubmissions may be made in response to these queries. The AIHW does not adjust data to account for possible data errors or missing or incorrect values, except as stated.
Although there are national standards for data on admitted patient care, statistics may be affected by variations in admission and reporting practices across states and territories.
There is apparent variation between states and territories in the use of statistical discharges and associated assignment of care types. For example, for public hospitals, the proportion of separations ending with a statistical discharge varied from 1.0% to 2.9% across states and territories.
For 2014–15, principal diagnosis information was not provided for 2,367 public hospital separations and 8 private hospital separations.
There was variation between states and territories in the reporting of separations for Newborns. For 2014–15:
  • For Victoria and the Northern Territory, private hospitals did not report all Newborn episodes without qualified days. Therefore, the count of newborns is underestimated.
While the Indigenous status data in the NHMD for all states and territories are considered of sufficient quality for statistical reporting for 2014–15, separations for Aboriginal and Torres Strait Islander people are under-enumerated. In 2011–12, about 88% of Indigenous Australians were identified correctly in hospital admissions data, and the ‘true’ number of separations for Indigenous Australians was about 9% higher than reported (AIHW 2013). Caution should be used in the interpretation of Indigenous status data because of the under-enumeration overall and differences in under-enumeration among the jurisdictions. The quality of the data for private hospitals is not known, but likely to be poor.
Not all states provided information on the area of usual residence of the patient in the form of a Statistical Area Level 2 (SA2) code for all presentations. Where necessary, the AIHW mapped the supplied area of residence data for each separation to an SA2 and to a remoteness area category based on Australian Bureau of Statistics (ABS) Australian Statistical Geography Standard (ASGS) correspondences and Remoteness Structures for 2011. This mapping was done on a probabilistic basis. Because of the probabilistic nature of the mapping, the SA2 and remoteness areas data for individual records may not be accurate and reliable; however, the overall distribution of records by geographical area is considered useful.
Socioeconomic status is based on the reported area of usual residence of the patient. The SEIFA categories for socioeconomic status are assigned at the national level, not at the individual state/territory level.


The AIHW provides a variety of products that draw upon the NHMD.
The Australian hospital statistics suite of products with associated Excel tables may be accessed on the AIHW website


Metadata information for the APC NMDS are published in the AIHW’s online metadata repository—METeOR, and the National health data dictionary.
METeOR and the National health data dictionary can be accessed on the AIHW website:

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