The remarks from Dr. Rest, coauthor of the recent guidelines on chronic fatigue syndrome [1], bear careful reflection because they touch on important and complex issues that are easily misunderstood.

The 1988 chronic fatigue syndrome working case definition [2] was revised to mitigate ambiguities and deficiencies that became apparent after field testing. The revised case definition remains a work in progress and not a "definitive" diagnostic tool. Thus, until an independent way to identify the syndrome is found, the validity of this or any similar case definition cannot be definitively established. Do these considerations negate the clinical value of defining such cases? Most emphatically not. Regardless of underlying cause, application of the chronic fatigue syndrome case definition identifies a clinically important group of patients requiring appropriate and compassionate medical attention. The guidelines provide concrete guidance for evaluating these persons.

The suggestion of the need for a definitive diagnostic tool for social purposes is confusing. Presumably, Dr. Rest is asserting that such a tool would make it easier for patients to address issues such as disability compensation on the basis of the syndrome. Is this true? We believe that the difficulties of addressing such issues are not fundamentally related to the diagnosis of the syndrome itself, but rather reflect the fact that our medical, legal, and social systems have yet to reach a consensus on how to regard a condition such as the chronic fatigue syndrome. Such a consensus is unlikely to arise unless current research efforts produce a larger body of reliable information on the syndrome.

Dr. Rotheram's comments reflect the deep frustration shared by many physicians and patients regarding the difficulty of assessing a condition that remains unconfirmable by independent tests. We are sympathetic with his dilemma; however, the evaluation and management of the syndrome require not only sound judgment but also inherent trust that what the patient has reported is, in some sense, valid. Descriptions of fatigue should be viewed no differently than other subjective reports, such as those of pain or nausea, that physicians are asked to evaluate.

We agree with Drs. Dodge and Kita that physicians who blindly emphasize what a patient cannot do as opposed to what a patient can do may reinforce a pattern of behavior that does not help the patient. Ignoring patient limitations, however, is equally as detrimental. As with any other chronic illness, maximization of a patient's ability to function as fully as possible is a cornerstone of therapy.