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"The Canadian Consensus Document should be read
and studied by every medical provider."
-David S. Bell, MD, FAAP- (USA)

This ME/CFS Clinical Working Case Definition provides the most comprehensive clinical guide currently available.  Health Canada selected an eleven member International Expert Consensus Panel who collectively "had diagnosed and/or treated more than twenty thousand patients.  There was 100% consensus by the panel members on the final Consensus Document.  The Consensus Document has become known as the Canadian Consensus Document for ME/CFS."  Also available is the excellent comprehensive yet concise Overview of the Canadian Consensus Document.

"The panel felt there was a need for the criteria to encompass more symptoms in order to reflect ME/CFS as a distinct entity and distinguish it from other clinical entities that have overlapping symptoms.  As fatigue is an integral part of many illnesses, the panel concurred that more other prominent symptoms should be compulsory."  This definition places the hallmark symptom of post-exertional malaise and neurological features as major criteria--much like the historic definitions, Ramsay's, Dowsett's, Hyde's and Hooper's descriptions of and definitional criteria for M.E.--unlike the US CDC and UK Oxford definitions that, in Elizabeth G. Dowsett's words, elevated "...glandular enlargement and fatigue to unreal importance, while overlooking the characteristic encephalitic features of the genuine illness [M.E.]."

Major criteria  in the Consensus Document that must be present are:

• "...a significant degree of new onset, unexplained, persistent, or recurrent physical and mental fatigue that substantially reduces activity level.

• "Post-Exertional Malaise and/or Fatigue: There is an inappropriate loss of physical and mental stamina, rapid muscular and cognitive fatigability, post exertional malaise and/or fatigue and/or pain and tendency for other associated symptoms with the patient's cluster of symptoms to worsen. The is a pathologically slow recovery period--usually 24 hours or longer.

• "Sleep Dysfunction:  There is unrefreshed sleep or sleep quantity or rhythm disturbances such as reversed or chaotic diurnal sleep rhythms.

• "Pain:  There is significant degree of myalgia.  Pain can be experienced in the muscles and/or joints, and is often widespread and migratory in nature.  Often there are significant headaches of new type, pattern or severity.

• "Neurological/Cognitive Manifestations:  Two or more of the following difficulties should be present:  confusion, impairment of concentration and short-term memory consolidation, disorientation, difficulty with information processing, categorizing and word retrieval, and perceptual and sensory disturbances--e.g., spatial instability and disorientation and inability to focus vision.  Ataxia, muscle weakness and fasciculations are common.  There may be overload phenomena [hypersensitivities to stimuli that have changed form pre-illness status]: cognitive, senory--e.g., photophobia and hypersensitivity to noise--and or emotional overload, which may lead to "crash" periods and or anxiety.

• "At Least One Symptom from Two of the Following Categories:
  Autonomic Manifestations
  Neuroendocrine Manifestations
  Immune Manifestations"

See the Overview of the Canadian Consensus Document a specific listing of these manifestations.)

This definition also includes a brief segment on ME/CFS in children.  (See also Pediatric ME/CFS)