Canadian Expert Consensus Panel Clinical Case Definition for ME/CFS
The Canadian Expert Consensus Panel has published a medical milestone, the
first clinical case definition for the disease known as myalgic
encephalomyelitis/chronic fatigue syndrome. This definition is clearly a vast
improvement over the CDC's 1994 Fukuda criteria, which led to misunderstanding
in both research and treatment modalities by making "fatigue" a compulsory
symptom but by downplaying or making optional the disease's hallmark of
post-exertional sickness and other cardinal ME/CFS symptoms. In sharp contrast
to the Fukuda criteria, this new clinical case definition makes it compulsory
that in order to be diagnosed with ME/CFS, a patient must become symptomatically
ill after exercise and must also have neurological, neurocognitive,
neuroendocrine, dysautonomic, and immune manifestations. In short, symptoms
other than fatigue must be present for a patient to meet the criteria. This case
definition, which incorporates some of the current research on dysautonomia,
cardiac, and immune problems, was published in the Journal of Chronic Fatigue
Syndrome, Vol. 11 (1) 2003.
For a 30-page excerpt of this document, which includes the diagnostic part of
the ME/CFS case definition in PDF format, click here.
PDF files require the use of an Adobe Acrobat Reader. If you do not already have
one, it is available as a free download
complete 109-page article "Myalgic Encephalomyelitis/Chronic Fatigue Syndrome:
Clinical Working Case Definition, Diagnostic and Treatment Protocols," J of
Chronic Fatigue Syndrome, Vol. 11 (1) 2003, pp. 7-116, from which the above
linked excerpt was taken, is available for a fee from the Haworth Document
Delivery Service -- 1-800-HAWORTH. The complete article contains valuable
information on treatment protocols and disability issues, as well as the full
references. The article can also be ordered on-line
It is summarized as follows:
1. POST-EXERTIONAL MALAISE AND FATIGUE: There is a loss of physical and mental stamina, rapid muscular and cognitive fatigability, post-exertional fatigue, malaise and/or pain, and a tendency for other symptoms to worsen. A pathologically slow recovery period (it takes more than 24 hours to recover). Symptoms exacerbated by stress of any kind. Patient must have a marked degree of new onset, unexplained, persistent, or recurrent physical and mental fatigue that substantially reduces activity level.
2. SLEEP DISORDER: Unrefreshing sleep or poor sleep quality; rhythm disturbance.
3. PAIN: Arthralgia and/or myalgia without clinical evidence of inflammatory responses of joint swelling or redness. Pain can be experienced in the muscles, joints, or neck and is sometimes migratory in nature. Often, there are significant headaches of new type, pattern, or severity. [Editorís note: neuropathy pain is a common symptom and should be added here as well.]
4. NEUROLOGICAL/COGNITIVE MANIFESTATIONS: Two or more of the following difficulties should be present: confusion, impairment of concentration and short-term memory consolidation, difficulty with information processing, categorizing, and word retrieval, intermittent dyslexia, perceptual/sensory disturbances, disorientation, and ataxia. There may be overload phenomena: informational, cognitive, and sensory overload -- e.g., photophobia and hypersensitivity to noise -- and/or emotional overload which may lead to relapses and/or anxiety.
5. AT LEAST ONE SYMPTOM OUT OF TWO OF THE FOLLOWING CATEGORIES:
AUTONOMIC MANIFESTATIONS: Orthostatic Intolerance: e.g., neurally
mediated hypotension (NMH), postural orthostatic tachycardia syndrome (POTS),
delayed postural hypotension, vertigo, light-headedness, extreme pallor,
intestinal or bladder disturbances with or without irritable bowel syndrome
(IBS) or bladder dysfunction, palpitations with or without cardiac arrhythmia,
vasomotor instability, and respiratory irregularities.
NEUROENDOCRINE MANIFESTATIONS: loss of thermostatic stability, heat/cold
intolerance, anorexia or abnormal appetite, marked weight change, hypoglycemia,
loss of adaptability and tolerance for stress, worsening of symptoms with stress
and slow recovery, and emotional lability.
IMMUNE MANIFESTATIONS: tender lymph nodes, sore throat, flu-like symptoms, general malaise, development of new allergies or changes in status of old ones, and hypersensitivity to medications and/or chemicals.
6. The illness persists for at least 6 months. It usually has an acute onset, but onset also may be gradual. Preliminary diagnosis may be possible earlier. The disturbances generally form symptom clusters that are often unique to a particular patient. The manifestations may fluctuate and change over time. Symptoms exacerbate with exertion or stress.
This summary is paraphrased from Dr. Kenny van DeMeirleir's book Chronic Fatigue Syndrome: A Biological Approach, February 2002, CRC Press, pg. 275. Again, for the 30-page diagnostic ME/CFS case definition click here.
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Last Updated: March 17, 2005