Data quality statement: National Hospital Morbidity Database 2011–12
Identifying and definitional attributes
|Metadata item type:||Quality Statement|
|Registration status:||AIHW Data Quality Statements, Archived 02/05/2014|
|Quality statement summary:|
This data quality statement provides information relevant to interpretation of the National Hospital Morbidity Database (NHMD) for 2011–12.Summary of key issues
• The National Hospital Morbidity Database (NHMD) is a comprehensive dataset that has records for all separations of admitted patients from essentially all public and private hospitals in Australia.
• 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.
• For 2011–12, almost all public hospitals provided data for the NHMD. The exception was a mothercraft hospital in the Australian Capital Territory. The great majority of private hospitals also provided data, the exceptions being the private free-standing day hospital facilities in the Australian Capital Territory, the single private free-standing day hospital in the Northern Territory, and a private free-standing day hospital in Victoria.
• Hospitals may be re-categorised as public or private between or within years.
• 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 0.9% to 3.9% across states and territories.
• There was variation between states and territories in the reporting of separations for Newborns (without qualified days).
• Data on state 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 2011–12, about 20% of separations for Australian Capital Territory hospitals were for patients who resided in New South Wales.
• Variations in admission practices and policies lead to variation among providers in the number of admissions for some conditions.
• Caution should be used in comparing diagnosis, procedure and external cause data over time, as the classifications and coding standards for those data can change over time. In particular, between 2009-10 and 2010–11, there were significant changes in the coding of diagnoses for diabetes and obstetrics and for imaging procedures.
• The Indigenous status data in the NHMD for all states and territories are considered of sufficient quality for statistical reporting for 2010–11 and 2011–12. In 2011–12, an estimated 88% of Indigenous patients were correctly identified in public hospitals. The overall quality of the data provided for Indigenous status is considered to be in need of some improvement and varied between states and territories.Description
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).
The counting unit for the NHMD is the ‘separation’. Separation is the term used to refer to the episode of admitted patient care, which can be a total hospital stay (from admission to discharge, transfer or death) or a portion of a hospital stay beginning or ending in a change of type of care (for example, from acute care to rehabilitation).
The NHMD contains records from 1993–94 to 2011–12. For each reference year, the NHMD includes records for admitted patient separations between 1 July and 30 June.
|Institutional environment:||Institutional environment
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 and Ageing 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 <www.aihw.gov.au>
Data for the NHMD were supplied to the AIHW by state and territory health authorities under the terms of the National Health Information Agreement (see the following link).
The state and territory health authorities received these data from public 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.
The reference period for this data set is 2011–12. This includes records for admitted patient separations between 1 July 2011 and 30 June 2012.
The agreed date for supply of a first version of data (based on best efforts) was 30 November 2012. Two states and territories provided a first version of 2011–12 data to the AIHW at the end of November 2012 and all had provided their first data by 19 December 2012. All states and territories had provided a final version of the data by 4 March 2013. The data were published on 19 April 2013.
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 <http://www.aihw.gov.au/hospitals/>
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:
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 3 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).
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 0.9% to 3.9% across states and territories.
For 2011–12, principal diagnosis information was not provided for approximately 3,000 public hospital separations and 1,000 private hospital separations.
There was variation between states and territories in the reporting of separations for Newborns (without qualified days). For 2011–12:
• Private hospitals in Victoria did not report most Newborn episodes without qualified days; therefore the count of newborns will be underestimated.
• South Australian private hospitals are not required to provide records for Newborn episodes without qualified days.
• For Tasmania, where a newborn’s qualification status was considered qualified at any point during the episode of care, the entire episode was reported as qualified days. As a consequence, the average length of stay for Newborn episodes with qualified days only in Tasmanian public hospitals is not directly comparable with that in other jurisdictions.
• The private hospital in the Northern Territory reported separations for Newborn episodes with qualified days that may not have involved qualified care.
While the Indigenous status data in the NHMD for all states and territories are considered of sufficient quality for statistical reporting for 2010–11 and 2011–12, 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 Local Area (SLA) code for all presentations. In addition, not all states and territories provided the version of SLA specified in the NMDS.
Where necessary, the AIHW mapped the supplied area of residence data for each presentation to the same SLA and to remoteness area categories based on the ABS ASGC Remoteness Structure for 2006. This mapping was done on a probabilistic basis. Because of the probabilistic nature of the mapping, the SLA 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 NHMD includes data for each reference year from 1993–94 to 2011–12.
The data reported for 2011–12 are broadly consistent with data reported for the NHMD for previous years.
Time series presentations may be affected by changes in admission practices, particularly for same-day activity such as dialysis, chemotherapy and endoscopy.
Between 2010–11 and 2011–12, there were substantial increases in counts of Newborn episodes of care with qualified days for New South Wales due to changes in reporting practices.
Changes in the ICD-10-AM/ACHI classifications and the associated Australian Coding Standards may affect the comparability of the data over time. In particular, between 2009-10 and 2010–11, there were significant changes in the coding of diagnoses for diabetes and obstetrics and for imaging procedures.
|Implementation start date:||05/07/2013|
Source and reference attributes
AIHW 2013. Indigenous identification in hospital separations data— Quality report. Cat. no. IHW 90. Canberra: AIHW.
|Related metadata references:|
Has been superseded by National Hospital Morbidity Database 2012-13 AIHW Data Quality Statements, Archived 03/06/2015
Supersedes National Hospital Morbidity Database Data Quality Statement: 2010-11 AIHW Data Quality Statements, Archived 05/07/2013