Incorporating severity of illness and comorbidity in case-mix measurement.

Three critical issues in determining the usefulness of a patient classification in hospital and physician payment, hospital management, and utilization monitoring include: 1) the clinical relevance of the categorization, 2) the extent to which severity of illness distinctions are incorporated, and 3) the identification of comorbidity. Each of these issues has been addressed in the design of patient-management categories, a clinically based patient classification developed by the Health Care Research Department of Blue Cross of Western Pennsylvania under Grant No. 18-P-97063/3-06 from the Health Care Financing Administration. This article describes the clinical specificity of patient-management categories, how their design and definition incorporates severity of illness, and how comorbid patients are differentiated from single disease patients having multiple related diagnoses.