Variation in resource use within diagnosis-related groups: the severity issue.

Several authors have suggested that diagnosis-related groups (DRG's) make inadequate allowance for the severity of illness. Before modifications of DRG's are developed, the sources of within-group variation must be precisely defined; not all variation is attributable to the severity of illness. The limitations of the Uniform Hospital Discharge Data Set (UHDDS), of the International Classification of Diseases, Ninth Revision, Clinical Modification coding system and of the original rules of DRG construction must be evaluated and, if necessary, corrected before new approaches to groupings are considered. The most promising potential modifications of existing groups and weights are those that make use of the UHDDS, or of the UHDDS plus additional diagnoses and procedures. The addition of entirely new data elements to the discharge abstract and the pricing process should be considered only as a last resort.