Doesn't it depend on how the term 'subset' and the term "CFS" are being used?
Here's my take. Sorry its long. Feel free to let me know where I am missing the point. I'd appreciate the feedback...
As a
lay person, I could correctly state that
multiple sclerosis "is a disease suffered by a subset of patients diagnosed each year with chronic fatigue syndrome." In this case, the term subset is being used in a common way to mean 'portion of' or 'some of'. The statement would be true - although potentially easy to misinterpret - because some 30% of MS patients have been shown to be given a diagnosis of CFS before they get a diagnosis of MS.
But the IOM is creating formal clinical diagnostic criteria for a disease/clinical entity. In that context I understand that the term subgroup has a stricter meaning that implies a relatedness to a larger group. For Multiple Sclerosis, one reference describes four subgroups based on the course of the disease - i.e. relapsing-remitting, progressive, etc. But they all have Multiple Sclerosis. Maybe as science progresses, they will determine that these are actually different diseases with very different pathways but for now they are considered subgroups of the same disease.
In the case of multiple sclerosis, these subgroups are related by clinical observations and diagnostic tests - that is, there is some rationale, scientific basis for grouping these four subgroups together as a clinical entity. Guessing they first started with the clinical entity and diagnostics and then flushed out the various subgroups.
My guess is that Jen is just speaking about a portion of patients that have the disease characterized by CCC/ME-ICC and not indicating that "ME" should be a formal subgroup of "CFS".
But IOM is planning on establishing formal subgroups so I think we need to first understand what clinical entity these diagnostic criteria are intended to describe. The IOM statement of work has included "CFS" but what does that mean? All the various conditions that meet Fukuda or Oxford? If so, the clinical entity is "6 months of debilitating fatigue that is medically unexplained, not relieved by rest and may have a variety of different causes including psychiatric causes" (my paraphrase).
So the first question is whether "CFS" - as defined above - is a valid clinical entity for which diagnostic criteria should be established? Have these various conditions ever been shown to have a common pathology underlying them? Are criteria of "Chronic Fatigue" + "Medically Unexplained" a rational foundation for a clinical entity? This is not an issue of the name "ME" versus "CFS" but whether the various criteria and conditions aggregated under the "CFS" label constitute a valid clinical entity to begin with. To the point that I think Delia made, if "CFS" is not a valid clinical entity to begin with, then how can there be legitimate subgroups?
I ran into these quotes recently that relate to this
- From Steven Straus of the NIH in a 1996 editorial praising the Report of the joint Royal Colleges on CFS
- "Neither the American [Fukuda] nor the Oxford criteria assume the [chronic fatigue] syndrome to be a single nosological entity."
- From Simon Wessely in a summary of the report of the joint Royal Colleges on CFS
- "Chronic Fatigue Syndrome (CFS) is not a single diagnostic entity."