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 an error DRG 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 a principal diagnosis. Diagnosis codes which are morphology codes cannot be used as a principal diagnosis.

A principal diagnosis should be recorded and coded upon separation, for each episode of admitted patient care or episode of residential care or attendance at a health care establishment. The principal diagnosis is derived from and must be substantiated by clinical documentation.

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

Australian Consortium for Classification Development

National Data Standard for Injury Surveillance Advisory Group