The number and percentage of patients with chronic disease--for whom the diagnosis is already known and for whom therapy is often simply the continuation of previously initiated interventions--are increasing. In such cases, because curative therapy is limited and the course of the disease is long, prognostication can become especially prominent. The clinical encounter is focused on the anticipation, avoidance, and mitigation of complications of the underlying disease itself or of the treatment. Patients with long-standing diabetes, for example, do not need to be told their diagnosis (which is known to them) or their therapy (for example, insulin--also known to them). Rather, they and their physicians are concerned with such questions as "Will my kidneys fail, and if so, when?" "Will I become blind?" "How long will I be able to care for myself?" "How long do I have to live?" Moreover, in chronic conditions, there is more opportunity to revise previously rendered prognoses as, over time, the physician learns more about the patient.

Several developments in health-care delivery and technology also support the increasing importance of prognosis. A key factor is the increasingly bureaucratic structure of American medical practice. More and more, physicians are becoming salaried employees beholden to bureaucratic management or are otherwise losing their economic independence and some of their professional autonomy. External review of physicians' clinical behavior often focuses on actions that are at least implicitly based on their prognostic judgments. For example, administrative oversight plays an increasing role in therapy management, as physicians are being asked, in the context of cost-effectiveness, to predict outcomes among a variety of (more or less) costly treatment options or to estimate the length of the hospital stay necessary for an anticipated medical outcome. Better prognostication, in the sense of a superior ability to foresee the outcome of a patient's illness, can help to optimize the choice of treatment and the timing of hospital admission, thus reducing costs.

A greater focus on prognosis also results from the increasing need to compare the quality of health-care providers, along with a societal interest in rationalizing health-care expenditures by directing resources to those most likely to benefit. Accurate and reliable prognostic assessments are central to identifying, developing, and implementing optimal health-care delivery systems in that they help patients and payers determine which systems lead to good or bad outcomes. In the same way, evaluating the cost-effectiveness of different medical therapies relies on access to accurate information about the probabilities of various outcomes, which are, in essence, prognoses. Some interventions may be cost-effective only in subpopulations where the patients are at particularly high or low risk of mortality, and payers may target interventions--conditional, again, on the patient's prognosis--to cases in which they feel the benefit justifies the cost. In each case, the ability to develop and analyze prognoses is essential to asking the right counterfactual questions and getting the right policy answers.

Another factor lending salience to prognosis is the increasing frequency of randomized, controlled clinical trials. The customary role of prognosis in clinical trials has been to ensure that patients of similar illness severity are compared, as groups of patients with an equivalent average prognosis (e.g., for death) are formed by the randomization process. However, rather than waiting for uncommon or temporally distant outcomes to occur in long-term clinical trials, which can be difficult and expensive, investigators are increasingly making use of "intermediate endpoints," that is, findings taken to be predictive of long-term outcomes. A decrease in a lab test is taken to indicate a decreased risk of eventual death, making shorter and less expensive trials possible. The booming industry in clinical trials thus supports increasing interest in the development and use of various prognostic staging systems and clinical markers.

The emergence of certain medical technologies also increases the relevance of prognosis. Such technologies--although often directed at improving diagnosis and therapy--also provide, directly or indirectly, more accurate and earlier prognostic information and therefore foster the rendering of prognoses. One example is obstetrical ultrasound, which may incidentally reveal information about the internal anatomy of a baby that would not otherwise be detected until well after the baby was born. Thus, parents and physicians are made aware of conditions long before the child is able to present with the illness. Such early findings, not yet corresponding to any observed symptom, demand explanation: patients wish to know what the findings will mean, what the future has in store. One pediatrician gives a typical example:

Nowadays, many kids come to our clinic when they're two weeks old because their kidneys were abnormal on Mom's prenatal ultrasound! In the old days when someone was diagnosed with polycystic kidney disease in the neonatal period, they died before they were one year old, but now there are so many much milder cases that only come to our attention because of an ultrasound that happens to have been done for other [obstetrical] reasons. We have no idea what to tell the parents about what to expect.…