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The diagnosis established after study to be chiefly responsible for occasioning an episode of admitted patient care, an episode of residential care or an attendance at the health care establishment, as represented by a code.


Data Element (this item)


Guide for use:

The principal diagnosis must be determined in accordance with the Australian Coding Standards. Each episode of admitted patient care must have a principal diagnosis and may have additional diagnoses. The diagnosis can include a disease, condition, injury, poisoning, sign, symptom, abnormal finding, complaint, or other factor influencing health status.

As a minimum requirement the Principal diagnosis code must be a valid code from the current edition of ICD-10-AM.

For episodes of admitted patient care, some diagnosis codes are too imprecise or inappropriate to be acceptable as a principal diagnosis and will group to 951Z, 955Z and 956Z in the Australian Refined Diagnosis Related Groups.

Diagnosis codes starting with a V, W, X or Y, describing the circumstances that cause an injury, rather than the nature of the injury, cannot be used as principal diagnosis. Diagnosis codes which are morphology codes cannot be used as principal diagnosis.


Health Data Standards Committee

National Centre for Classification in Health

National Data Standard for Injury Surveillance Advisory Group

The principal diagnosis is one of the most valuable health data elements. It is used for epidemiological research, casemix studies and planning purposes.


Bramley M, Peasley K, Langtree L and Innes K 2002. The ICD-10-AM Mental Health Manual: an integrated classification and diagnostic tool for community-based mental health services. Sydney: National Centre for Classification in Health, University of Sydney
This content Based on Australian Institute of Health and Welfare material. Attribution provided as required under the AIHW CC-BY licence.

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Relation Count
Inclusion in Data Set Specifications 12
Inclusion in Data Distributions 0
As a numerator in an Indicator 18
As a denominator in an Indicator 2
As a disaggregation in an Indicator 4