The parents ask for predictions. They want to know when will the kid need dialysis, when will they have to start thinking about transplant, when will this kidney disease that we see on the ultrasound affect them, because right now their kids are thriving, they're doing well. But at some point they're going to need erythropoeitin shots and growth hormone and vitamin D and all these different things that we see with renal failure. We have no idea when that will be.

The advent of genetic-testing technology provides an important new arena for prognostication. Analysis of a person's genes may reveal relevant medical outcomes years or decades in advance in what are generally termed "presymptomatic carriers." In contrast to other tests applied for diagnostic purposes, these tests have specifically prognostic importance, which is made all the more apparent by the fact that, in most cases, no specific interventions are available to cure the condition so detected, or even to delay its onset. A prototypic example is Huntington's disease, a fatal, degenerative neurological disease that usually begins in the patient's forties. Tests can now reveal with certainty, decades before any symptoms are noted, whether asymptomatic individuals will or will not develop the disease. Because no treatment is available for the condition, this is an example of the phenomenon of the complementary relationship between therapy and prognosis, in that the prognostic significance of these tests eclipses their therapeutic utility.

In other situations, genetic tests are used to develop prognostic information that does have therapeutic implications. For example, some women, on the basis of the prognostic information provided by genetic tests to evaluate their risk for breast cancer, undergo prophylactic mastectomy--even though this prognosis is not certain. As more studies reveal genetic bases for diseases as diverse as emphysema, diabetes, dementia, cognitive disability, and alcoholism, the prognostic use of genetic tests will certainly rise. The use of such tests is also likely to rise outside of medical arenas, for example, in law.

The increasingly technological, "postclinical" nature of medical practice fosters the availability of information that is presymptomatic in nature, and therefore inherently prognostic. "Presymptomatic" illness is, indeed, the specifically prognostic analog of "asymptomatic" illness. The notion of asymptomatic or "occult" or "silent" illness is itself interesting in that it posits a phenomenological realm of disease of which the patient has no subjective experience. This realm requires the intercession of an expert, a physician, to be comprehended. Typically, the expert must use technology to approach this realm, as when the physician uses diagnostic tests to adduce the presence of disease even when the patient has no symptoms.

The implications of the notion of presymptomatic disease, however, extend even beyond those of asymptomatic disease. Rather than indications of an already present disease, the expert is said to have discovered indications of a disease that is not yet even present. Some physicians have even begun to call individuals whose genetic tests are positive for a worrisome gene "prepatients." The notion of presymptomatic illness thus represents an even further distancing of the patients' subjective experience of disease from the everyday practice of medicine. Moreover, the term presymptomatic suggests an inexorable outcome: the patient will eventually develop symptoms.

The application of new technologies to patient care increases the importance of prognostication in one other way: it creates a whole new class of things about which to prognosticate, namely the complications of the technology. Beneficial new technologies in medicine-from computed tomography to chemotherapy to open heart surgery-have not come without risk. Predicting their consequences is important, and doctors are frequently called upon to explain to patients a potentially confusing array of possible outcomes.

In addition to changes in types of medical problems people face and in the ways physicians confront them, there have been changes in how patients and physicians think about the ethical duties of physicians to their patients. Prognosis is a fundamental, though implicit, basis for many theoretical and practical ethical decisions in medical care, and prognostic uncertainty may complicate such decisions considerably. Ethical decision making is increasingly finding its way to the bedside. The elaborate informed consent process that patients undergo before having procedures or participating in research, for example, is predicated upon predicting risks and benefits. Prognosis also profoundly affects decisions to initiate, withhold, or terminate life support for critically ill newborns and adults, and it figures in the discussions about these decisions that doctors have with patients' families. Prognostication is critical when one must allocate scarce medical resources to those patients for whom they can do the most good.

Finally, it is central to the notion of "futility," a concept usually invoked in situations where death is predicted to be imminent and inevitable. The relatively recent emergence of futility as a theme in bioethics reflects the moral desirability of acknowledging medical limitations and the practical necessity of allocating scarce resources. Futility is based on a prognosis not only that the patient is unlikely to recover spontaneously, but also that any intervention will likely be ineffective. As the avoidance of futile treatment has assumed increasing prominence, for reasons of justice, beneficence, or economy, prognostication--which is, after all the fundamental and essential basis for a determination of futility--has increased in importance.

Broad changes in American society are influencing the doctor-patient relationship and fostering an increased interest in prognosis. In areas from childbearing to terminal care, patients want information about expected outcomes that they can use to manage their care actively. This is especially true with respect to care at the end of life. Now, physicians have the duty to inform their patients about their illness, and patients have a right to know.

In recent years, the American public has become more focused on planning for death, a development reflected in the increasing interest in everything from living wills to physician-assisted suicide. There has been a profusion of books on caring for the terminally ill at home, which include vivid, nontechnical descriptions of what to expect and which document the impact of death on family members. There have been best-selling how-to books on "self-deliverance." And there have been books describing the process of dying, often using detailed and intimate case histories. These latter books typically reflect an attempt to help people find meaning in dying, and they suggest that death is increasingly viewed as a passage that can be actively anticipated and therefore managed. To enact these popular visions of death, however, patients must rely on reasonably accurate prognoses from professional physicians.

Ongoing changes in the nature of illness in contemporary American society, as well as in the way medical problems are being confronted, have substantially increased the relevance of prognostication in clinical care. As these trends converge, the nation's physicians will increasingly be expected to prognosticate--they may be reluctant prophets, but they will be prophets nonetheless.