The NSW Combined Admitted Patient Epidemiology Data (CAPED) records all inpatient separations (e.g. discharges, transfers and deaths) from all public, private, psychiatric and repatriation hospitals in NSW, as well as public multi-purpose services, private day procedure centres and public nursing homes. The CAPED includes data on hospital admissions of NSW residents which occurred in public hospitals interstate.

In CAPED, Public Hospital data are recorded in terms of episodes of care. An 'episode of care' ends with the patient ending a period of stay in hospital (e.g. by discharge, transfer or death) or by becoming a different 'type' of patient within the same period of stay. For private hospitals, each CAPED record represents a complete hospital stay. CAPED records are counted based on the date of separation (discharge) from hospital.

Imputation of interstate admissions in recent data

Data from interstate hospitals for the latest year 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 the latest year of hospitalisations based on interstate admissions in the preceding  year. Interstate admissions records from the previous year are copied into the file for the most recent year, 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 latest year.  

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 Health System Information and Performance Reporting Branch 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) published by the National Centre for Classification in Health. 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.

Overnight and day-only hospital stays are included

Unless otherwise specified, both overnight and day-only hospitalisations are included in HealthStats NSW. National reporting on hospital statistics (AIHW, 2015) do not include day-only hospitalisations.

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 the latest year 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 the latest year of hospitalisations based on interstate admissions in the preceding  year. Interstate admissions records from the previous year are copied into the file for the most recent year, 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 latest year.  

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, 2015) do not include day-only hospitalisations.

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 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. Australian hospital statistics 2013–14. Health services series no. 60. Cat. no. HSE 156. Canberra: AIHW, 2011. Available at http://www.aihw.gov.au/publication-detail/?id=60129550483

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.