Web update: Potentially preventable hospitalisations in 2015–16 - Technical Note - Potentially preventable hospitalisations in 2015–16

Web update: Potentially preventable hospitalisations in 2015–16

Potentially preventable hospitalisations in 2015–16

This technical note accompanies Web update: Potentially preventable hospitalisations in 2015–16.

The web update presents local rates of selected potentially preventable hospitalisations (PPH). These are conditions where hospitalisation could have potentially been prevented through the provision of appropriate, preventive health interventions and early disease management usually delivered in primary care and community-based care settings (including by general practitioners, medical specialists, dentists, nurses and allied health professionals). PPH rates are indicators of the effectiveness of non-hospital care. The rate of PPH in a local area may reflect the prevalence and severity of the conditions, or effectiveness and access to the non-hospital care system.

There are three broad categories of PPHs:

  1. Vaccine-preventable—diseases that can be prevented by vaccination. In this update, they are grouped as pneumonia and influenza (vaccine-preventable) and other vaccine-preventable conditions. Other vaccine-preventable conditions include:

    • chicken pox
    • diphtheria
    • haemophilus meningitis
    • hepatitis
    • measles
    • mumps
    • pertussis (whooping cough)
    • polio
    • rubella
    • tetanus
  2. Acute—conditions that theoretically would not result in hospitalisation if adequate and timely care (usually non-hospital) was received. These include:

    • cellulitis
    • convulsions and epilepsy
    • dental conditions
    • ear, nose and throat infections
    • eclampsia
    • gangrene
    • pelvic inflammatory disease
    • perforated/bleeding ulcer
    • pneumonia (not vaccine-preventable)
    • urinary tract infections (including kidney infections)
  3. Chronic—conditions that can be managed effectively through timely care (non-hospital) to prevent deterioration and hospitalisation or through behaviour modification and lifestyle changes. These include:

    • angina
    • asthma
    • bronchiectasis
    • chronic obstructive pulmonary disease (COPD)
    • congestive heart failure
    • diabetes complications
    • hypertension
    • iron deficiency anaemia
    • nutritional deficiencies
    • rheumatic heart diseases

Results are presented for the 31 Primary Health Network (PHN) areas that cover Australia, and for more than 300 smaller local areas called Statistical Areas Level 3 (SA3s), as defined by the Australian Bureau of Statistics (ABS) in 2011.

About the data source

Data for the web update were sourced from the AIHW National Hospital Morbidity Database (NHMD). The NHMD is a compilation of episode-level records from admitted patient morbidity data collections in Australian hospitals. The NHMD includes all episodes of care for admitted patients, including admissions for day only care, in nearly all public and private hospitals. The NHMD does not include episodes of non-admitted patient care provided in outpatient clinics or emergency departments. Episodes for unqualified newborn care, and records of posthumous organ procurement or hospital boarders are excluded.

In the web update, the counting unit is a ‘hospitalisation’ (or separation). This may be a complete hospital stay (to discharge, transfer, or death), or a part of the stay if there was a change of care type (for example from acute care to rehabilitation). As a record is included for each hospitalisation, not for each patient, patients hospitalised more than once or transferred between hospitals in the financial year will have more than one record.

Comparability over time

Caution should be used when comparing PPH over time, due to changes in coding, geographic concordances and admission practices which are outlined below.

Information presented over time may be affected by changes to codes and coding standards defined in the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD-10-AM)1 and the Australian Classification of Health Interventions (ACHI).2 The major changes affecting the interpretation of information presented in the web update are outlined below.

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 AIHW examined data provided for 2015–16. The number of potentially preventable hospitalisations with a care type of Rehabilitation increased substantially, with the majority of the increase seen in the chronic conditions: congestive heart failure, diabetes complications and COPD.

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 vaccine-preventable hospitalisations.

For more information about these issues, see Data Quality Statement Summary, pages 238–263, Admitted patient care 2015–16: Australian hospital statistics.External link, opens in a new window.[http://www.aihw.gov.au/reports/hospitals/admitted-patient-care-2015-16-australian-hospital-statistics/]3

Data reported in previous PPH releases (National Health Performance Authority reports Healthy Communities: Potentially preventable hospitalisations in 2013–14 (released in 2015) and Healthy Communities: Selected potentially avoidable hospitalisations in 2011–12 (released in 2013)) were calculated by applying a geographic concordance from postcode rather than Statistical Area Level 2, which may affect comparability with the current release.

In addition, changes in admission policies and practices over time and by area may impact on comparability. For more information about these issues see Healthy Communities: Potentially preventable hospitalisations in 2013–14.4

About the measures

Indicator measure

Age-standardised rate of potentially preventable hospitalisation

Data for this measure were prepared for the Performance and Accountability (PAF) indicator Selected potentially avoidable hospitalisations. This is defined in accordance with the National Healthcare Agreement (NHA) indicator PI 18-Selected potentially preventable hospitalisations, but is reported at PHN area and SA3 level. State and national-level results are available in the publication Admitted patient care 2015–16: Australian hospital statistics.External link, opens in a new window.[http://www.aihw.gov.au/reports/hospitals/admitted-patient-care-2015-16-australian-hospital-statistics/]3

For a detailed list of the codes used to define each of the conditions reported, see the Appendix.

Data source
Data sources

Australian Institute of Health and Welfare, National Hospital Morbidity Database (NHMD)

Australian Bureau of Statistics (ABS) Estimated Resident Population (ERP)

Indicator description
Type of measurement Age-standardised rate per 100,000 population, reported as an integer.
Method of adjustment Direct age-standardisation.5 The standard population used was the ABS ERP at 30 June 2001.
Numerator Number of hospitalisations for each of the conditions as specified in the Appendix. All care types (e.g. acute, rehabilitation) are included.
Denominator ABS ERP at 30 June 2015
Calculation (Numerator ÷ denominator) × 100,000 (age-standardised)
Geographic assignment SA2 of residence reported at the following levels:
  • Primary Health Network (PHN) area
  • Statistical Area Level 3 (SA3).
Indicator disaggregation Rates are reported for the 22 conditions listed in the Appendix, and for the following categories of conditions:
  • All PPH
  • Chronic
  • Acute
  • Vaccine-preventable
  • Acute and vaccine-preventable

Contextual measure

The web update includes a number of other measures to provide context to the indicator measure:

Number of potentially preventable hospitalisations
Calculated as the number of hospitalisations for each of the conditions as specified in the Appendix.

Crude rate of potentially preventable hospitalisations
Calculated as the number of potentially preventable hospitalisations divided by the ABS ERP at 30 June 2015, multiplied by 100,000.

Number of same day hospitalisations
Calculated as the number of potentially preventable hospitalisations where the admission and separation occur on the same date.

Percentage of potentially preventable hospitalisations that are same day
Calculated using the number of same day potentially preventable hospitalisations divided by the total number of potentially preventable hospitalisations, multiplied by 100 and rounded to one decimal place.

Number of potentially preventable hospitalisation bed days
Calculated as the sum of the number of days from admission to separation for all relevant hospitalisations. Same day hospitalisations are allocated one bed day and leave days are excluded.

Average length of stay
Calculated as the number of bed days divided by the number of hospitalisations, including same day hospitalisations, rounded to one decimal place.

About the methods

Geography

The web update presents information at the geography of:

  • Primary Health Network (PHN) areas – 31 geographic areas covering Australia, with boundaries defined by the Australian Government Department of Health6
  • Statistical Areas Level 3 (SA3s) – 333 geographic areas covering Australia, with boundaries defined by the ABS.7

Using the Statistical Area Level 2 (SA2) of usual residence in the NHMD unit record data, rather than the location of the hospital where each patient was admitted, data by geographic area were calculated by applying a geographic concordance from SA2 to PHN area and SA3 area. Where an SA2 boundary overlapped a PHN area, records were attributed to a PHN area based on the percentage of the population within that SA2 that fell within each PHN area. Figures were rounded at the end of the calculations.

In tables presenting measures by geographic area, individual area results may not add to national totals due to missing location data, and also due to rounding.

Principal and additional diagnoses

Each hospitalisation in the NHMD is coded with a principal diagnosis and up to 50 additional diagnoses. The principal diagnosis is the diagnosis established after study to be chiefly responsible for occasioning an episode of admitted patient care. An additional diagnosis is a condition or complaint either coexisting with the principal diagnosis or arising during the episode of admitted patient care.

Most PPH were identified from their principal diagnosis. However there were four PPH conditions identified using either principal or additional diagnoses. These were:

  1. Pneumonia and influenza (vaccine-preventable)
  2. Other vaccine-preventable conditions
  3. Pneumonia (not vaccine-preventable)
  4. Gangrene.

In tables presenting measures by PPH condition, some hospitalisations may account for multiple PPH conditions. As a result, conditions may not sum to categories, and categories may not sum to total PPH. For example, a hospitalisation with a principal diagnosis of vaccine-preventable pneumonia and an additional diagnosis of gangrene will be reported in the vaccine-preventable category to reflect pneumonia, and the acute category to reflect gangrene.

For a detailed list of the codes used to define each of the conditions reported, see the Appendix

Age-standardisation

The web update includes measures expressed as age-standardised rates per 100,000 population. Age-standardised rates are hypothetical rates that would have been observed if the populations studied had the same age distribution as the standard population. This facilitates comparisons between populations with different age structures. This adjustment is important because the rates of many health conditions vary with age.

The direct method of age-standardisation was applied to the data.5 Age-standardised rates were derived by calculating crude rates by five year age groupings of 0–4 years to 85+ years. If a patient‘s age was recorded as over 116, they were excluded. These crude rates were then given a weight that reflected the age composition of the standard population. The current standard population is the ABS Estimated Resident Population for Australia as at 30 June 2001.

Suppression of results

All data for an area were suppressed (marked ‘Not available for publication’) if the number of rounded potentially preventable hospitalisations was less than 5 for an area.

Crude rates were suppressed if:

  • the number of potentially preventable hospitalisations (numerator) was less than 20 for an area, or
  • the population of an area (denominator) was less than 2,500.

Age-standardised rates were suppressed if either of the suppression conditions for crude rates were met. For the remaining rates, if the population of an area (denominator) was less than 30 in any of the standard 5-year age groupings used to calculate the rate, then the rate was marked ‘Interpret with caution’ as these rates are considered potentially more volatile than other published rates. For each of these flagged rates, the effect of an increase of one hospitalisation on the rank of the area was examined. If the rank changed so much that the area was on the cusp of changing two deciles, then the rate was suppressed (marked ‘Not available for publication’).

Results for number of same day hospitalisations, percentage of potentially preventable hospitalisations that are same day, number of potentially preventable hospitalisation bed days, and average length of stay were suppressed if either of the suppression conditions for crude rates were met, or the number of same day hospitalisations was between one and four for an area.

1 ACCD (Australian Consortium for Classification Development) 2014. The International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM)—9th edn.—tabular list of diseases, and Alphabetic index of diseases. Sydney: Independent Hospital Pricing Authority.

2 ACCD 2015. The Australian Classification of Health Interventions (ACHI)—9th edn.—Tabular list of interventions, and Alphabetic index of interventions. Sydney: Independent Hospital Pricing Authority.

3 AIHW (Australian Institute of Health and Welfare) 2017. Admitted patient care 2015–16: Australian hospital statistics. Health services series no.75. Cat. no. HSE 185. Canberra: AIHW.

4 NHPA (National Health Performance Authority) 2015. Healthy Communities: Potentially preventable hospitalisations in 2013–14. Sydney: NHPA.

5 AIHW 2005. Age-standardised rate. Canberra: AIHW. Viewed 8 March 2017, http://meteor.aihw.gov.au/content/index.phtml/itemId/327276External link, opens in a new window.

6 Department of Health 2016. Primary Health Networks (PHNs). Canberra: Department of Health. Viewed 4 May 2017, http://www.health.gov.au/internet/main/publishing.nsf/Content/PHN-HomeExternal link, opens in a new window.

7 ABS (Australian Bureau of Statistics) 2011. Australian Statistical Geography Standard (ASGS): Volume 1—Main structure and greater capital city statistical areas, ABS cat. no. 1270.0.55.001. Canberra: ABS.