New Criteria for Myalgic Encephalomyelitis / Chronic Fatigue Syndrome Unveiled

Karen Lee Richards Health Guide
  • Last week the Journal of Internal Medicine published “Myalgic Encephalomyelitis: International Consensus Criteria” online ahead of the print version.  The new criteria was developed by an impressive panel of 26 ME/CFS experts from 13 different countries.  Notably, there was 100% agreement among panel members on the final criteria presented.

    Two of the many controversies that have swirled around ME/CFS (myalgic encephalomyelitis / chronic fatigue syndrome) for years are what to call it and how to diagnose it correctly. 

    The Name

    What to call this illness has been the subject of numerous disagreements in the ME/CFS community.  You can read more about the many name iterations in “A Disease in Search of a Name: The History of CFS and the Efforts to Change Its Name.” 

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    I was pleasantly surprised to see that the consensus panel, in the first three sentences of the abstract, attempted to settle the argument once and for all. 

    “The label “chronic fatigue syndrome” (CFS) has persisted for many years because of lack of knowledge of the etiological agents and of the disease process. In view of more recent research and clinical experience that strongly point to widespread inflammation and multisystemic neuropathology, it is more appropriate and correct to use the term “myalgic encephalomyelitis”(ME) because it indicates an underlying pathophysiology. It is also consistent with the neurological classification of ME in the World Health Organization’s International Classification of Diseases (ICD G93.3).” 

    The Criteria

    A disease criteria serves several functions:

    • It defines the illness.
    • It makes research both possible and more accurate by grouping patients with a specific set of similar symptoms together.
    • It can often be used to help diagnose patients. 

    Over the years, a number of different criteria have been used for ME/CFS.  The problem is that some, like the Reeves Empirical Criteria, are so broadly inclusive that a large number of patients with Major Depressive Disorder end up being included, which significantly skews the results of any research done using that criteria. 

    Following is the new International Consensus Criteria:

    A patient 

    • will meet the criteria for post-exertional neuroimmune exhaustion (A), 
    • will have at least one symptom from three neurological impairment categories (B), 
    • will have at least one symptom from three immune/gastro-intestinal/genitourinary impairment categories (C), and 
    • will have at least one symptom from energy metabolism/transport impairments (D).


    A. Post-Exertional Neuroimmune Exhaustion (PENE pen ׳-e) 
    This cardinal feature is a pathological inability to produce sufficient energy on demand with prominent symptoms primarily in the neuroimmune regions. 
    Characteristics are:

    1.  Marked, rapid physical and/or cognitive fatigability in response to exertion, which may be minimal such as activities of daily living or simple mental tasks, can be debilitating and cause a relapse. 

  • 2.  Post-exertional symptom exacerbation: e.g. acute flu-like symptoms, pain and worsening of other symptoms.
    3.  Post-exertional exhaustion may occur immediately after activity or be delayed by hours or days.

    4.  Recovery period is prolonged, usually taking 24 hours or longer. A relapse can last days, weeks or longer. 

    5.  Low threshold of physical and mental fatigability (lack of stamina) results in a substantial reduction in pre-illness activity level.

    B. Neurological Impairments 
    At least one symptom from three of the following four symptom categories: 
    1.  Neurocognitive Impairments 

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    a.  Difficulty processing information: slowed thought, impaired concentration e.g. confusion, disorientation, cognitive overload, difficulty with making decisions, slowed speech, acquired or exertional dyslexia.

    b.  Short-term memory loss: e.g. difficulty remembering what one wanted to say, what one was saying, retrieving words, recalling information, poor working memory.
    2.  Pain

    a. Headaches: e.g. chronic, generalized headaches often involve aching of the eyes, behind the eyes or back of the head that may be associated with cervical muscle tension; migraine; tension headaches .

    b.  Significant pain can be experienced in muscles, muscle-tendon junctions, joints, abdomen or chest. It is non-inflammatory in nature and often migrates. e.g. generalized hyperalgesia, widespread pain
    (may meet fibromyalgia criteria), myofascial or radiating pain.
    3.  Sleep Disturbance 

    a.  Disturbed sleep patterns: e.g. insomnia, prolonged sleep including naps, sleeping most of the day and being awake most of the night, frequent awakenings, awaking much earlier than before illness onset, vivid dreams/nightmares.
    b.  Unrefreshed sleep: e.g. awaken feeling exhausted regardless of duration of sleep, day-time sleepiness
    4.  Neurosensory, Perceptual and Motor Disturbances 

    a.  Neurosensory and perceptual: e.g. inability to focus vision, sensitivity to light, noise, vibration, odour, taste and touch; impaired depth perception.
    b. Motor: e.g. muscle weakness, twitching, poor coordination, feeling unsteady on feet, ataxia.

    C. Immune, Gastro-intestinal & Genitourinary Impairments 
    At least one symptom from three of the following five symptom categories:
    1.  Flu-like symptoms may be recurrent or chronic and typically activate or worsen with exertion. e.g. sore throat, sinusitis, cervical and/or axillary lymph nodes may enlarge or be tender on palpitation.
    2.  Susceptibility to viral infections with prolonged recovery periods.
    3.  Gastro-intestinal tract: e.g. nausea, abdominal pain, bloating, irritable bowel syndrome.
    4.  Genitourinary: e.g. urinary urgency or frequency, nocturia.
    5. Sensitivities to food, medications, odours or chemicals

    D. Energy Production/Transportation Impairments 
    At least one symptom:
    1.  Cardiovascular: e.g. inability to tolerate an upright position – orthostatic intolerance, neurally mediated hypotension, postural orthostatic tachycardia syndrome, palpitations with or without cardiac arrhythmias, light-headedness/dizziness.


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    2.  Respiratory: e.g. air hunger, laboured breathing, fatigue of chest wall muscles.
    3.  Loss of thermostatic stability: e.g. subnormal body temperature, marked diurnal fluctuations; sweating episodes, recurrent feelings of feverishness with or without low grade fever, cold extremities.
    4.  Intolerance of extremes of temperature.


    In addition to the above criteria, the paper identifies four subgroups based on symptom severity.  Symptom severity impact must result in a 50% or greater reduction of a patient’s premorbid activity level for a diagnosis of ME.

    • Mild – approximately 50 percent reduction in activity
    • Moderate – mostly housebound
    • Severe – mostly bedbound 
    • Very Severe – bedbound and dependent on help for physical functions

    My Thoughts...

    I could not be happier to see this paper.  Not only does it clearly state that 'myalgic encephalomyelitis' is a “more appropriate and correct” name than 'chronic fatigue syndrome' for this illness, but it presents a reasonable, well-researched set of criteria by which ME can be accurately identified and diagnosed. 

    One feature of other ME/CFS criteria that is conspicuously absent from the International Consensus Criteria is the six-month waiting period.  Other criteria require that patients have ME/CFS symptoms for six months before they can be diagnosed.  Personally, I've always had a problem with the six-month requirement.  As the authors of the paper noted, “No other disease criteria require that diagnoses be withheld until after the patient has suffered with the affliction for six months.”  The waiting period does a huge disservice to patients since early treatment may lessen the severity of the illness. 

    Now I just hope this new International Consensus Criteria will gain widespread acceptance around the world, including our own U.S. Centers for Disease Control and Prevention (CDC).  Agreement on the criteria used in research should give us much more consistent results than we've seen in the past.  Fingers crossed!  

    You can download the full text of this paper here:  “Myalgic Encephalomyelitis: International Consensus Criteria”  (Note: This text has not yet been copy-edited and corrected for print publication.)
    Carruthers BM, et al. Myalgic Encephalomyelitis: International Consensus Criteria. J Intern Med. 2011 Jul 20. [Epub ahead of print]


Published On: July 27, 2011