Diagnoses or conditions that affect a person's care in terms of requiring:
- therapeutic treatment
- clinical evaluation
- diagnostic procedure
- extended length of hospital stay; or
- increased nursing care and/or monitoring.  

Additional diagnoses include:
- co-morbid conditions, that is, co-existing conditions; and/or
- complications, that is, conditions that arose during the episode of care.

Additional diagnoses give information on factors which result in increased length of stay, more intensive treatment or the use of greater resources.  They are required  for casemix analyses relating to the severity of illness and for correct classification of patients into Australian National Diagnosis Related Groups.