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.
 
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.

Subgroups

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.)
_______________
Source:
Carruthers BM, et al. Myalgic Encephalomyelitis: International Consensus Criteria. J Intern Med. 2011 Jul 20. [Epub ahead of print]