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January 3, 2001

Diagnosing and Defining Disease

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JAMA. 2001;285(1):89-90. doi:10.1001/jama.285.1.89-JMS0103-2-1

The patient and his wife are seated when the doctor enters the room. They are holding hands; the heel of his foot taps erratically against the leg of his chair. The doctor closes the door behind him while glancing at his chart.

"Mr Richardson, Mrs Richardson, how do you do? Sorry to keep you waiting. It's been a busy morning."

"No, no, it's no problem, Doctor." The patient laughs nervously. "I've been waiting two years to find out what's wrong with me. A couple of minutes . . . " he trails off and shrugs.

"I know what you mean." Pages rustle as the doctor flips through the chart. "Well, you know, when you first came in to see me, I was as confused about your symptoms as you. Maybe more." He looks up and smiles ironically—patient and wife nod politely but do not smile back. "But with these test results and the changes you've been noticing over the last few months, I think we have a better idea of what's going on. Mr Richardson, I think that you have a condition that we call . . . "

The patient and his wife lean forward slightly, eyes wide: an image of pregnant anticipation.

What happens when a patient is given a diagnosis? A diagnosis is, first of all, a description of the patient as a sufferer of a particular disease process. A diagnosis can also be an explanation for patients who have had symptoms but do not know their cause. Giving a name to the problem may seem to resolve the mystery, such that even patients with intractable, chronic diseases may feel relief when diagnosed. And of course, a diagnosis often offers a prediction about the future course of illness, or about the genetic or infectious risk to others.

All of the above belong to what might be considered the "science" of medicine—but diagnosing diseases has more subtle implications as well. Identifying a disease can confer social legitimacy on a patient's symptoms, relieving patients of the suspicion that they are malingering or exaggerating their woes1,2; conversely, it may be seen to imply that the patient is somehow abnormal or requires intervention. Having a disease might mark the patient as a member of a community of sufferers, as demonstrated by the many patient and family associations that exist for various illnesses. Finally, diagnosing a disease can have important legal and economic consequences, such as conferring eligibility for disability benefits or even (in the case of the insanity defense) exempting patients from responsibility for their actions.

Thus, while diseases are commonly thought to be scientifically defined, the naming and diagnosis of diseases is also a social practice with implications that extend beyond the clinic doors. We might wonder, given these pressures, if "disease" is truly a unified concept. Some diseases, such as tuberculosis or embolic stroke, identify a highly specific etiologic agent or process; others, like Alzheimer disease or scleroderma, indicate pathologic changes of unclear cause; while syndromes and functional disorders simply describe collections of symptoms and signs that frequently occur together. What do these labels all have in common?

This question is complicated because there is a tension in medical concepts of health and disease. On one hand, they are meant to represent objective, scientific facts—this patient is healthy, that patient has disease. But on the other hand, they also involve evaluative judgments about good and bad—a healthy state is better than a diseased state, a diseased state is in some way abnormal or dysfunctional—that are more than matters of simple scientific fact. To illustrate: when a patient is diagnosed with coronary artery disease, part of what is implied is that subendothelial accumulations of lipids and macrophages are present in his or her coronary arteries, increasing the likelihood of coronary ischemia, and these are more or less objective descriptions. But another part of what is implied is that the patient has a disease, an abnormality that results in impairment of his or her quality of life, and this is an evaluative judgment.

"Quality of life" is a telling phrase, because it reveals how concepts like health and disease, function and dysfunction, are interwoven with conceptions of the good life. As Caplan et al3 note, "what will count as minimal standards of function or as special levels of excellence will depend on value judgments concerning what is important to be able to do as a human being." Indeed, ideas about what counts as health and disease have changed to fit changes in value judgments and therapeutic options. For instance, contraception is now thought of as part of medical care because the medical community considers it important for people to plan and control reproduction, while physicians of an earlier time would have considered reproduction to be the necessary physiologic function of sex. Impotence was once considered by most people to be simply an unfortunate occurrence, but with less problematic therapies it is now considered a treatable medical condition. Both of these changes reflect changed cultural attitudes about the role of sex and sexuality in human life.

Thus, the concept of health involves a descriptive component (what someone is able to do) as well as an evaluative component (what it is important to be able to do, in order to be able to live a good life). Similarly, the concept of disease involves a duality between a description (a physiological or functional difference between the patient and the "healthy" norm) and an evaluation (the judgment that this difference is abnormal or dysfunctional, and not just different). However, this duality is obscured in everyday practice, in part due to the scientific aspirations of medicine and scientific assumptions built into the medical model.

For instance, consider the standard "SOAP" progress note, in which the patient's report of symptoms is termed "subjective," while physical findings and laboratory results are termed "objective." This subjective/objective distinction is based on a standard understanding of scientific observation, in which the subjective corresponds to how things seem from a particular perspective (in this instance, the patient's experience) while the objective corresponds to concepts that are not tied to any particular point of view (such as temperature or the concentration of ions in the blood). In Western science, the subjective and objective are often reconciled by a "reduction," in which the subjective appearance is explained by reference to the objective account of how things "really are."4 The classic example is the Copernican heliocentric model of the cosmos, in which the subjective appearance that the sun travels around the earth is explained by an objective description of the earth orbiting the sun.

Medical practice employs a related model in the notion of a "disease entity," inherited in large part from the scientific aspirations of earlier physicians such as Koch and Virchow.5 In this model, diseases are conceptualized as distinct, objective entities that are common to afflicted patients. While the patient often cannot directly perceive the presence of the disease entity itself (such as a microorganism or histologic change), the patient does perceive the subjective symptoms that are caused by its presence. Thus, the subjective symptoms are explained by reference to objective changes in the body, in much the same way that subjective appearances in the physical world are explained by reference to objective concepts such as matter, energy, and force.

The disease entity model has had great success in explaining the symptoms associated with infectious diseases, certain cancers, and poisons, which are understood as distinct entities and which often produce a "classic" set of symptoms and signs in the afflicted patient. These are widely taken as ideal examples of disease processes, and they influence a paradigm in which physicians are seen (or see themselves) as disease-hunting scientists or detectives collecting data to identify the etiologic agent. (For instance, it is not surprising that most of the vivid short pieces in Berton Roueché's classic The Medical Detectives6 involve bacteria, parasites, and poisons.) This paradigm then structures the expectations of patients and physicians. Both may see the physician as someone who can or should provide "answers" to the patient's problems, and both can be frustrated when this expectation is not met.

This paradigm is less well suited to multifactorial conditions, such as type 2 diabetes mellitus and coronary artery disease, which are thought to result from the overlap of various contributing factors rather than a single etiologic agent. Still, in these diseases there are objective findings that can confirm and explain the patient's subjective feelings of illness, so the subjective/objective distinction is preserved. More problematic are functional disorders, syndromes of unclear etiology (such as chronic fatigue syndrome and fibromyalgia), and complaints that do not fit any recognized symptom complex. In these cases, there may be no objective findings to confirm and explain the patient's subjective feelings of illness—the subjective feeling of illness is all there is. Physicians may then feel pressured by the seriousness of the patient's complaints to give a diagnosis that they privately regard as scientifically unsubstantiated; and some have worried that giving names that pretend to explain poorly-understood complaints may have the unintended effect of creating new illnesses, as with the "transient mental illnesses" studied by philosopher Ian Hacking.7 For the patients' part, they may feel that without the legitimacy conferred by a recognized medical diagnosis, the severity of their symptoms and even their own sincerity will be doubted.

What these tensions suggest is that rather than debating whether or not these syndromes and functional disorders are "real" or "legitimate" medical conditions, scrutiny should instead focus on conventional models of disease and the standard assumptions that patients and physicians bring to the medical encounter. The presumption that disabilities and functional limitations are less real in the absence of an independently observable disease entity reflects an assumption that all real medical conditions must follow the same paradigm. Yet the possibility remains that the modes of explanation appropriate to illnesses like infections and poisons may not be applicable to more complex complaints, such as those involving interactions between mind, body and culture. The tensions felt by many physicians and patients suggest that new modes of characterizing medical problems are needed.

Rosenberg  CE Framing disease: illness, society, and history. Rosenberg  CEed.Framing Disease: Studies of Cultural History New Brunswick, NJ Rutgers University Press1992;13- 26
Groopman  J Hurting all over. New Yorker. November13 2000;78- 92
Caplan  ALEngelhardt  HTMcCartney  JJ Introduction. Caplan  ELEngelhardt  HTMcCartney  JJeds.Concepts of Health and Disease: Interdisciplinary Perspectives Reading, Mass Addison-Wesley1981;23- 31
Nagel  T The View From Nowhere.  New York, NY Oxford University Press1986;
Engelhardt  HT The concepts of health and disease. Caplan  ELEngelhardt  HTMcCartney  JJeds.Concepts of Health and Disease: Interdisciplinary Perspectives Reading, Mass Addison-Wesley1981;31- 46
Roueché  B The Medical Detectives.  New York, NY Truman Talley Books/Plume1991;
Hacking  I Mad Travelers.  Charlottesville University Press of Virginia1998;