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Principal diagnosis cubes for 1993–94 to 2014–15

The principal diagnosis is defined as the diagnosis established after study to be chiefly responsible for occasioning the patient’s episode of care in hospital. In some cases, the principal diagnosis is described in terms of a treatment for an ongoing condition (for example, care involving dialysis or rehabilitation).

Data source

The source of these data is the AIHW National Hospital Morbidity Database. Other data on the principal diagnosis reported for admitted patients are available in the Australian hospital statistics reports. Some data have been revised since previously published. For confidentiality, some data have been suppressed.


Data cubes will open in a new window.

The use of the different editions in the data cubes means that data across years may not be exactly comparable.

The variables in the data cubes are:

  • Year
  • Sex (Male, Female, Other/Not reported)
  • Age group (5 year groupings, i.e. <1, 1–4, 5–9,10–14,...85+, Not reported)
  • Same day (Same day/non-same day)
  • Principal diagnosis

The measures (values ) in the data cubes are:

  • Total separations
  • Patient days
  • Average length of stay (ALOS)

Within the cubes, users can view the diagnoses by using a pull-down menu and can work down from the broad chapter level in the ICD classifications to more specific categories (i.e. principal diagnosis code), as illustrated below:

  • ICD Chapter
  • ICD Sub-Chapter
  • ICD 3-character code
  • ICD 4-character code (where relevant)
  • ICD 5-character code (where relevant)

For example:

  • Endocrine, nutritional and metabolic diseases (E00-E89)
  • Impaired glucose regulation and diabetes mellitus (E00-E14)
  • Type 2 diabetes mellitus (E11)
  • Type 2 diabetes mellitus with circulatory complication (E11.5)
  • Type 2 diabetes mellitus with diabetic cardiomyopathy (E11.53)

Users of the data cubes are likely to require some familiarity with ICD-9-CM and ICD-10-AM and have access to the full publications. This data access system does not allow searching on keywords or ICD-9-CM/ICD-10-AM codes. Users will generally need to know what chapter the information they are looking for is in, to work down to more specific levels of detail. 

International Classification of Diseases (ICD)

Principal diagnoses are classified according to either the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) or the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD-10-AM). The use of the different classifications (ICD-9-CM and ICD-10-AM) in the data cubes means that data for 1998–99 to 2013–14 may not be exactly comparable with data for 1993-94 to 1997-98.

In addition, there are some differences in the coding between editions and these will be reflected in the cube. Readers should refer to the National Centre for Classification in Health (NCCH) for information on how to access the full classification and for detailed information on the differences between ICD-9-CM, ICD-10-AM and the different editions of ICD-10-AM.

The following is a list of the ICD disease chapters and the code ranges covered by each:

Chapter Disease classification Code range
1 Certain infectious and parasitic diseases A00–B99
2 Neoplasms C00–D48
3 Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism D50–D89
4 Endocrine, nutritional and metabolic diseases E00–E90
5 Mental and behavioural disorders F00–F99
6 Diseases of the nervous system G00–G99
7 Diseases of the eye and adnexa H00–H59
8 Diseases of the ear and mastoid process H60–H95
9 Diseases of the circulatory system I00–I99
10 Diseases of the respiratory system J00–J99
11 Diseases of the digestive system K00–K93
12 Diseases of the skin and subcutaneous tissue L00–L99
13 Diseases of the musculoskeletal system and connective tissue M00–M99
14 Diseases of the genitourinary system N00–N99
15 Pregnancy, childbirth and the puerperium O00–O99
16 Certain conditions originating in the perinatal period P00–P96
17 Congenital malformations, deformations and chromosomal abnormalities Q00–Q99
18 Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified R00–R99
19 Injury, poisoning and certain other consequences of external causes S00–T98
20 External Causes of Morbidity and Mortality U50–Y98
21 Factors influencing health status and contact with health services Z00–Z99


In order to maintain confidentiality, some data have been suppressed. This has been applied at the three-digit/character level for the principal diagnosis data cubes.

Data have been suppressed for a particular diagnosis if:

  • there is a potential risk of identifying an individual
  • there are fewer than three reporting units (hospitals or states/territories where the hospitals are not individually identified), or
  • there are three reporting units and one contributed more than 85% of the total separations, or
  • there are three or more reporting units and two contributed more than 90% of the total separations.

Data for the suppressed categories will not appear in the data cubes, but will be included in the sub-chapter, chapter and grand totals. Thus, the sum of separation counts presented within a chapter or sub-chapter for some codes may not match the total. 

Link to AR-DRG and procedures data cubes