Severity of illness. Red herring or horse of different color? Part 1

This article, the first in a three-part series, describes the theoretical underpinnings of the production of health and the measurement of health care effectiveness and provider performance. It defines severity of illness, discusses the proposed uses of severity scores, and provides criteria for validating severity measurement systems. The present use of severity scores to adjust outcomes simply assumes their validity, an obvious and inherent flaw. They do not and cannot measure the quality of care. Costs are determined by the provider's response to, and the preferences of, the patient. Use of severity scores either to adjust outcomes or to determine payment for care denies the legitimacy of patients' preferences.