Measuring Severity of Illness: Homogeneous Case Mix Groups

In this article we evaluate a new severity of illness index for use in defining case mix groupings of hospitalized patients. We find that this index, which takes into account patient severity of illness, produces groups that are more homogeneous (with respect to total charges, length of stay, routine charges, and laboratory charges) than those produced by four other case mix grouping methods that do not reflect the total burden of the patient's illness. These results have important implications for programs of prospective reimbursement and for cross-hospital comparison studies.