The gravity of a patient’s condition. Patients with the same diagnosis often vary from being mildly ill to being extremely ill, or even dying. Under the prospective payment system (PPS), every patient with the same diagnosis (actually, every patient within a given diagnosis related group (DRG), of which there are only 468) is given the same “price tag.” No allowance is made for the severity of the patient’s illness. Efforts are underway to persuade the federal government to make such an allowance, and other efforts are being made to develop practical methods for quantifying “severity of illness” so that it can be reliably incorporated in the mathematics of the pricing formula. Such quantification is referred to as developing a “severity index” or “score.” The stimulus for severity measures is illustrated, for example, by the fact that a diabetic patient in coma (very severely ill) understandably should cost more to treat than one hospitalized simply to “finetune” the control of the diabetes. Note that a measure of severity on admission to the hospital, followed by another later measure, permits evaluation of the patient’s progress under care, while a measure which can only show severity on discharge does not permit this interpretation.