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I have a great deal of respect for Dr Jason and am impressed with his body of work. I think the issue with the paper in question is how one identifies "true CFS" without objective measures. Comparing the empirical, Fukuda, and CCC by whether they identify "true CFS" is dependent on the list of symptoms the researcher decides define "true CFS". "True CFS" at this point is a construct based on opinions, so any definition can be said to best identify "true CFS". It was a valiant effort, but doomed to sloppy subjectiveness without an objective marker that defines the illness. It was probably the best that could be done at the time with the information currently available. That doesn't mean it is highly accurate.
I was trying to be clear that I was distinguishing a more specific definition of the illness -- ME, from the broader classification CFS. For my purposes, ME is defined by the ICC and includes carefully defined PEM/PENE (not exercise intolerance) as a requirement along with neurological, immune, and energy metabolism symptoms. Fukuda, and even the CCC (which is an ME/CFS definition, not an ME definition) are less specific. That does not mean that they don't identify a currently unidentified serious illness, but simply that they are less specific and include a broader group of patients. Whether the broader group is a more or less accurate representation of the illness is as yet unknown.
It may be that we will find that Fukuda or the CCC catch more "true" patients because they will include more patients in the early stages or with mild versions while the ICC only catches patients with longer-term or more severe cases of the same illness. This happened with AIDS. The AIDS definition excluded most HIV positive patients because they hadn't developed the serious symptoms that defined AIDS, so no one knew they had the same illness until the virus was identified and doctors realized that many more people had the virus than had AIDS. We could be in a similar situation. We won't know until we get an objective measure and define the illness as those who meet that measure. That may exclude many people we now consider PWME and include others we wouldn't think of as PWME now. There is no true definition of this illness without a clear understanding of the pathophysiology, which we don't have at the moment.
It is generally accepted in medical research that the best way to identify the features of an illness is to start looking at the clearest and most extreme cases. Once you've identified what makes that group distinctly different from healthy people, you have a unique measure you can use to start looking at broader patient groups to see if that measure exists in them as well. We need that in CFS as well -- research done on smaller specific subsets to try to tease out what identifies the illness or illnesses subsumed under the ridiculously broad CFS umbrella.
ICC-ME is one of those subsets. There are likely other subsets that can be identified by symptoms (GI symptoms/no GI symptoms, OI/no OI), or objective measures (specific immune profiles, failed CPET test). Eventually we'll sort out which subsets are part of the same illness and which are different illnesses. But until we accept that CFS by Oxford or Fukuda subsumes too many different conditions to be a single illness, we will continue to have inconclusive research.
The requirement that at least four of these physical symptoms be present concurrently rules out most cases of mental illness.
I disagree. The following symptoms can all be part of mental illnesses
- post-exertion malaise lasting more than 24 hours (if you include exercise intolerance or "fatigue" as PEM, which many doctors do)
- unrefreshing sleep
- significant impairment of short-term memory or concentration
- muscle pain
- headaches of a new type, pattern, or severity
So a patient with primary mental illness could easily meet Fukuda with 4 of the above symptoms. Yes, it rules out most cases of mental illness, but it still includes many, which is simply not good enough, imo. There are millions upon millions of people with mental illness. Excluding most of them still can leave a large number, possibly even a majority of the group compared to the relatively few ME patients, still under the CFS umbrella distorting research into features and treatments.
Fukuda also subsumes OI-only conditions and primary sleep disorders under CFS. Fukuda is simply too broad to be catching a single condition. That does not mean it is not identifying patients with serious conditions that need attention, just that it is probably not identifying a single illness. If you don't believe me, do a little experiment. Search for illnesses that include the Fukuda symptom list. You won't get only one illness, especially if you only use 4 of the most common symptoms -- poor sleep, memory or concentration problems, headaches, muscle or joint pain. Those alone will collect a huge number of patients with conditions other than the very specific ICC-defined ME, and many of them won't even have what most of us would recognize as ME/CFS, or even CFS.
I never said Fukuda was worthless. I said it is a very broad umbrella definition that includes a large number of fatiguing conditions which make it difficult, if not impossible, to tease out the specific illnesses subsumed under the CFS heading. We know this already by the vague results of research using the Fukuda definition. All researchers find is that CFS is a heterogeneous condition with no clear patterns. Well duh! It's like taking the entire population of a city, looking for symptoms of pregnancy, and then claiming there's no such thing as pregnancy because there is no consistent pattern of pregnancy in the group as a whole. That doesn't mean there aren't useful and interesting subgroups in the large population -- men, children, non-pregnant women -- it just means you can't identify the features of a specific condition if your sample set is too broad. Fukuda is. It simply doesn't work as a research definition because is cannot identify a single condition, or even a couple of closely related conditions.
I cannot accept that Fukuda uniquely defines ME. The simple fact that is does not require PEM/PENE is enough for me. That doesn't mean that Fukuda CFS does not include ME, just that it includes many other conditions as well. That is, an ME patient will meet the Fukuda definition, but a Fukuda CFS patient will not necessarily be an ME patient.
IMO, CFS and ME are not completely different illnesses, nor are they equivalent. They are set and subset.