Hospital statistics in NSW
All NSW public hospitals, public psychiatric hospitals, public multi-purpose services, private hospitals and private day procedure centres in NSW report data on patients admitted for care to the NSW Ministry of Health. The NSW Ministry of Health also receives data relating to NSW residents hospitalised in public hospitals interstate.
These data are held in the Health Information Exchange (HIE) maintained by the System Information and Analytics Branch (SIA) within the NSW Ministry of Health.
Population and public health reporting using the Combined Admitted Patient Epidemiology Data
The Centre for Epidemiology and Evidence, NSW Ministry of Health, maintains the Combined Admitted Patient Epidemiology Data (CAPED) in the SAPHaRI (Secure Analytics for Population Health Research and Intelligence) data warehouse. These data are extracted from the HIE and provide a dataset for reporting on population and public health in NSW.
Defining 'hospitalisations' for the purpose of reporting
Principal diagnosis and additional diagnoses coded to ICD-10-AM
Each hospital episode in CAPED is described by a principal diagnosis and additional diagnoses, which are coded using the International Statistical Classification of Diseases and Related Health Problems: ICD-10-AM.
In HealthStats NSW, the count of hospitalisations for a condition is on the principal diagnosis unless specified otherwise. For indicators pertaining to injury and poisoning hospitalisations, the count is based on ‘external cause of injury’.
Procedures coded to Australian Classification of Health Interventions
Procedures performed in Australian hospitals are coded in medical records using the Australian Classification of Health Interventions (ACHI) were published by the National Centre for Classification in Health and are now published by the Independent Hospital Pricing Authority (IHPA). This classification is based on the Commonwealth Medicare Benefits Schedule and relates to anatomy rather than surgical specialty.
On 1 July 1998, both the ACHI and the ICD-10-AM were introduced in NSW. They are revised every two years. The ICD-10 is the World Health Organization classification but the AM suffix stands for Australian Modification, which adds detail necessary to describe practice in Australian hospitals. The ICD-10-AM is fully compatible with ICD-10 (NCCH 2006).
Up to the fourth edition of ICD-10-AM in 2004, the ACHI was published as a part of the ICD manuals (volume 3 and 4). From the fifth edition in 2006 the titles of the ACHI publication emphasise that this is a classification independent from the ICD.
Episode-of-care–based count of hospitalisations
Unless otherwise specified, the count of hospitalisations in HealthStats NSW is based on an episode of care. A patient can have several episodes of care during one hospital stay, that is, between the formal admission and the formal discharge (separation) from hospital.
The episode of care is defined by a service category. An episode of care starts when the hospital stay starts or when the service category changes. There are 10 service categories: acute care, rehabilitation, palliative care, maintenance care, newborn care, other care, geriatric evaluation and management, psychogeriatric care, organ procurement–posthumous, and hospital boarder.
A new episode of care starts also when a patient is on leave from hospital: more than 4 days away from any hospital and more than 10 days away from psychiatric hospitals.
Separation date determines the year of hospitalisation
The main record file of the hospital stay for a patient is created or completed on separation from hospital when all relevant documentation is made available to hospital medical record departments. Consequently the main reason for hospitalisation (principal diagnosis), completed at separation, may be different from the admitting diagnosis. The hospitalisation is counted in the year the separation took place even if the hospitalisation period occurred predominantly in the previous financial year. For example, a patient discharged on 1 July after a 4 week hospital stay would be counted as hospitalised in the new financial year.
Imputation of interstate hospitalisations in the latest years of data
Data from interstate hospitals for recent years may not yet be available when the data are analysed for publication. This may affect analyses and has a greater effect on rates for areas closer to an interstate boundary. Analyses by geographical regions and analyses involving uncommon diagnoses or procedures are particularly affected. Therefore, an estimate is made of interstate admissions for recent years of hospitalisations based on interstate admissions in the most recent year for which interstate data are available. Interstate admissions records from the most recent year for which interstate data are available are copied into the file for the most recent years, assuming that the attributes of these admissions (such as sex, age, geography, type of diagnosis or procedure) provide the best predictor of those for admissions in the recent years.
Differences between figures published by the AIHW, the NSW Ministry of Health and other institutions
Differences in publication schedules
Data in the HIE is continuously updated because it is not uncommon to receive additional records or additional information on records already supplied well after the close of a financial year. Data in CAPED is regularly updated to reflect the most recently available information in the HIE. Consequently data on hospitalisations in NSW from different sources, such as HealthStats NSW and the AIHW report, will always differ slightly due to different publication schedules.
Definition of hospitalisation
Unless otherwise specified, both overnight and day-only hospitalisations are included in HealthStats NSW. National reporting on hospital statistics (AIHW, 2020) do not include day-only hospitalisations.
Patients treated solely within the emergency department are excluded from this indicator report due to a policy change (PD2017_015). Please note that a minority of patients being managed in short stay areas of emergency departments are still included. Further information is found in a paper in HealthStatsPLUS Methods on this website.
Different projected populations
For the calculation of rates, the NSW Ministry of Health uses population projections based on the population projections prepared by the NSW Department of Planning Infrastructure and Environment. Refer to the Methods in Population topic for further information on projected populations and other issues mentioned here. The rates in HealthStats NSW are expressed as a number per 100,000 population.
Rates published by the Australian Institute of Health and Welfare may be expressed differently (per 1,000 or 10,000 population) and use different projected population estimates for NSW. The population estimates, which are not projected, are likely to be the same, as these are based on the estimated residential populations published by the Australian Bureau of Statistics.
References
Australian Institute of Health and Welfare. Australia’s hospitals at a glance 2018–19. Cat. no. HSE 247. Canberra: AIHW, 2020. Available at https://www.aihw.gov.au/reports/hospitals/australias-hospitals-at-a-glance-2018-19/summary
National Centre for Classification in Health. The International statistical classification of diseases and related health problems, 10th Revision, Australian Modification (ICD-10-AM). Australian Coding Standards. Sydney: NCCH, 2006.