A casemix for mental health services: the development of the mental health and substance abuse components of the Australian national diagnosis-related groups.

Objective: To describe the development of the mental health and substance abuse sections of the version of the Australian casemix system, Australian national diagnosis-related groups 3 (AN-DRG 3), released in July 1995. Method: The guiding principles and data sources used to construct the mental health and substance abuse components of AN-DRG 3 are described by the group who undertook that task, The group used data sets of patients separating from hospitals throughout Australia, and from hospitals in South Australia, to examine the capacity of existing and revised diagnosis-related groups (DRGs) to predict patients' lengths of hospital stay, They also reviewed the lists of conditions allowed as complicating and comorbid conditions within the AN-DRG system. Results: A variety of recommendations were made including: moving organic mental disorder DRGs to a neuroscience area of the AN-DRG; completely reorganising the mental health section of the casemix; creating a number of narrowly defined DRGs covering areas such as schizophrenia, major affective disorders, anxiety disorders and eating disorders, while allowing for a limited number of more heterogenous DRGs; and simplifying substance abuse DRGs into groups covering alcohol and other substances, and differentiating intoxication and withdrawal from abuse and dependency. Conclusions: A casemix dialect based on clinical diagnosis, which describes mental health and substance abuse problems in terms which should be familiar to clinicians, has been developed, Its applications and limitations are briefly discussed.