Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a multisystem and often long-lasting disorder, with manifestations that can cause substantial morbidity and can severely impair patients’ health and well-being. It is estimated that between 836 000 and 2.5 million individuals are affected in the United States. Patients with ME/CFS are typically unable to perform their normal activities, and as many as one-fourth are homebound or bedridden, sometimes for extended periods. As a result, the personal and social effects and ramifications of this disease are enormous.
However, ME/CFS is poorly accepted and poorly understood, and the characteristics necessary to make the diagnosis are contested. Patients’ concerns are often met with dismay and skepticism, if not outright dismissal. Clinicians, in turn, are confronted by competing definitions, which were usually developed for research and are quite complex and difficult to implement in a busy clinical practice. Patients who are fortunate enough and persistent enough to receive a correct diagnosis frequently report long delays before their disorder was identified. It is almost certainly the case that the majority of affected patients are never diagnosed. This is unfortunate because effective symptom management is often available, whereas the wrong interventions can make symptoms worse.
Making the diagnosis is essential for providing appropriate care. To that end, the Department of Health and Human Services (HHS), together with the National Institutes of Health, US Social Security Administration, US Food and Drug Administration, Centers for Disease Control and Prevention, and Agency for Healthcare Research and Quality, tasked the Institute of Medicine (IOM) to develop “evidence-based clinical diagnostic criteria for ME/CFS for use by clinicians, using a consensus-building methodology,” with input from patients and clinicians; to “recommend whether new terminology for ME/CFS should be adopted”; and to create plans for disseminating these conclusions to clinicians. To meet its charge, the IOM committee heard testimony from patients, clinicians, and researchers, carefully reviewed almost one thousand public comments, and conducted a comprehensive literature review. Currently available evidence permitted the committee, in its newly released report, to identify symptoms and findings that collectively identify the disorder for which a new name was proposed, as discussed below. These criteria are set forth in the accompanying Box.
IOM Diagnostic Criteria for Systemic Exertion Intolerance Disease
Diagnosis requires that the patient have the following 3 symptoms:
- A substantial reduction or impairment in the ability to engage in preillness levels of occupational, educational, social, or personal activities that persists for more than 6 months and is accompanied by fatigue, which is often profound, is of new or definite onset (not lifelong), is not the result of ongoing excessive exertion, and is not substantially alleviated by rest AND
- Postexertional malaise* AND
- Unrefreshing sleep*
At least 1 of the 2 following manifestations is also required:
- Cognitive impairment* OR
- Orthostatic intolerance
* Frequency and severity of symptoms should be assessed. The diagnosis of systemic exertion intolerance disease (myalgic encephalomyelitis/chronic fatigue syndrome) should be questioned if patients do not have these symptoms at least half of the time with moderate, substantial, or severe intensity.