Note: See also the page on Fibromyalgia. Many patients with ME/CFS also have Fibromyalgia.

 CRITERIA FOR DIAGNOSING ME/CFS

According to the Canadian Consensus Criteria (CCC) defined by an international panel of experts in 2003.

The CCC and its overview documents are available on our resources page

1. FATIGUE: The patient must have a significant degree of new onset, unexplained, persistent, or recurrent physical and mental fatigue that substantially reduces activity level and is usually made worse by exercise.

2. 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 a tendency for other associated symptoms within the patient's cluster of symptoms to worsen. There is a pathologically slow recovery period - usually 24 hours or longer.

3. SLEEP DYSFUNCTION: There is unrefreshed sleep or sleep quantity or rhythm disturbances such as reversed or chaotic diurnal sleep rhythms.

4. PAIN: There is a significant degree of myalgia. Pain can be experienced in the muscles and/or joints, and is often widespread and migratory in nature. The pain may also have neuralgic qualities. Often there are significant headaches of new type, pattern or severity.

5. 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,
• 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: cognitive, sensory- e.g. photophobia and hypersensitivity to noise - and/or emotional overload, which may lead to "crash" periods and/or anxiety.

6. AT LEAST ONE SYMPTOM FROM TWO OF THE FOLLOWING CATEGORIES:

a) AUTONOMIC MANIFESTATIONS:

orthostatic intolerance - neurally mediated hypotension, postural orthostatic tachycardia syndrome, delayed postural hypotension; light-headedness; extreme pallor; nausea and irritable bowel syndrome; urinary frequency and bladder dysfunction; palpitations with or without cardiac arrhythmias; exertional dyspnea.

b) NEUROENDOCRINE MANIFESTATIONS:

loss of thermostatic stability - subnormal body temperature and marked diurnal fluctuation, sweating episodes, recurrent feelings of feverishness and cold extremities; intolerance of extremes of heat and cold; marked weight change  anorexia or abnormal appetite; loss of adaptability and worsening of symptoms with stress.

c) IMMUNE MANIFESTATIONS:

Tender lymphnodes, recurrent sore throat, recurrent flu-like symptoms, general malaise, new sensitivities to food, medications and/or chemicals.