Using computerised patient-level costing data for setting DRG weights: the Victorian (Australia) cost weight studies.

Casemix-funding systems for hospital inpatient care require a set of resource weights which will not inadvertently distort patterns of patient care. Few health systems have very good sources of cost information, and specific studies to derive empirical cost relativities are themselves costly. This paper reports a 5 year program of research into the use of data from hospital management information systems (clinical costing systems) to estimate resource relativities for inpatient hospital care used in Victoria's DRG-based payment system. The paper briefly describes international approaches to cost weight estimation. It describes the architecture of clinical costing systems, and contrasts process and job costing approaches to cost estimation. Techniques of data validation and reliability testing developed in the conduct of four of the first five of the Victorian Cost Weight Studies (1993-1998) are described. Improvement in sampling, data validity and reliability are documented over the course of the research program, the advantages of patient-level data are highlighted. The usefulness of these byproduct data for estimation of relative resource weights and other policy applications may be an important factor in hospital and health system decisions to invest in clinical costing technology.