Meeting research versus clinical criteria: Table 1
provides all the symptoms as specified in the Revised
Canadian ME/CFS case definition. Some meet full
criteria whereas others who are very symptomatic do
not meet full criteria. We argue as we did with the
Pediatric case definition (Jason et al., 2006) that those
that meet full criteria are more homogenous and might
be best used for research purposes and we now classify
these individuals as meeting the Research ME/CFS
criteria. Still, others might have the illness but not meet
one of the required criteria. We classified such
individual as meeting Clinical ME/CFS criteria. These
individuals needed to have six or more months of
fatigue and needed to report symptoms in five out of the
six ME/CFS symptom categories (one of which has to
be post exertional malaise, as it is critical to this case
definition). In addition, for autonomic, neuroendocrine
and immune manifestations, adults must have at least
one symptom in any of these three categories, as
opposed to one symptom from two of the three
categories. We also have a category called Atypical
ME/CFS, which is defined as six or more months of
fatigue, but having two to four ME/CFS symptoms.
There is also a category called ME/CFS-Like, which
involves exhibiting all criteria categories but for a
duration of fewer than 6 months. Further, a person
could be classified as having ME/CFS in remission if
the person had previously been diagnosed with CFS by
a physician but was not currently meeting the Research
ME/CFS Criteria, Clinical ME/CFS criteria, or Atypical
ME/CFS criteria and must have 0 or 1 classic ME/CFS
symptoms.