Thanks to my good buddy Steve for this one:
Re: Tom Kindlon's post yesterday regarding Dr. Reeves
remarks, we know that we have very good studies to argue
against the Dr. Reeves remarks.
Dr. Leonard Jason wrote excellent counter arguments to
Dr. Reeves' "empirical definition"
Also, from the IACFS-M. E. Conference
Jason, L., Porter, N and N. Najar. Evaluating the CDC
criteria for an empirical case definition.
The CDC believes that the Fukuda definition is so vague 'that it is
essentially impossible to compare results between studies critically"
and that this definition has contributed to difficulty CFS
researchers have in replicating study findings.
Two years ago the International CFS Working Group (ICWG) convened by
the CDC recommended that the Fukuda definition be revised to better
characterize the fatigue, disability and symptom severity found in
CFS. The ICWG suggested that several different tests be used; the CDC
took two of them (SF-36, MFI) and added one of its own (Symptom
inventory) and then came up with criteria it proposed would
differentiate CFS from CFS-like patients. These tests consist of a
series of questionnaires that examine different aspects of fatigue
(mental, physical, etc.), disability (mental, physical, emotional,
etc.), etc. People scoring at the 25th percentile or lower on one of
the questionnaires from each of the tests are deemed to have CFS. The
CDC now uses this definition to determine which patients it will
include in its CFS studies.
Except for the symptom index, the tests in the new definition are
standardized tests used to measure fatigue and disability in diseases
for many years. Dr. Reeves is proposing that if you are fatigued and
disabled to some extent and have a certain symptom profile and don't
have any other diseases, then by definition you have CFS.
This new definition is a radical departure from past definitions.
Other attempts at a CFS definition have focused solely on finding the
right symptom profile for CFS and a consensus has emerged in North
America regarding how CFS presents itself symptomatically; the
Canadian Consensus and the IACFS Pediatric definitions are remarkably
similar. The CDC clearly believes that symptoms cannot be used to
differentiate CFS patients from CFS-like patients and it has some
evidence for this - a large study that attempted to do so failed.
Dr. Jason, however, pointed out that several of the questionnaires in
the SF-36 and MFI concentrate solely on emotional or mental aspects
of fatigue and disability. Two SF-36 questionnaires focus on
emotional problems and mental health and one MFI questionnaire
focuses on reduced motivation. This suggests that under the new CDC
criteria fatigued people with emotional problems but not necessarily
with the physical components of CFS could meet the criteria for CFS
and participate in CFS studies. In a small study Dr. Jason found that
40% of patients with major depression qualified for CFS.
This, of course, suggests that future CFS studies by the CDC could
have an increased component of patients with depression or other mood
disorders. This may already have happened; the recent Heim study
employing the empirical definition found that 62% of the sample had
evidence of early childhood abuse of one type or another. This
contrasted with a study employing the Fukuda criteria that did not
find high levels of childhood abuse. It bears noting, however, that
people diagnosed with major depression (with melancholia or
psychosis) in the last five years are excluded from participating
from CFS studies under the new definition.
Dr. Jason also argued that these criteria were developed more or less
arbitrarily; that they were derived using judgments rather than
scientific analysis. This was rather ironic given the fact that
arbitrariness was one of the arguments Dr. Reeves used against the
Fukuda definition. Although the components of the empirical
definition were vetted by another international group, the definition
itself was not. Indeed it appears to have been developed much like
the Fukuda definition, as Dr. Reeves put it, by a small group of
people (Dr. Reeves and his research team) in a 'smoke-filled room'.
In the definition paper Dr. Reeves and his team acknowledged that
"one could debate our choice of specific subscales¼ .and the specific
cutoff values we chose".
The definition of CFS ought to be a biomarker and Dr. Jason suggests
that it be identified and undergo rigorous testing to ensure that a)
it includes those that have CFS and b) it does not include those that
do not have it. The CDC has shown that empirical definition does a
better job than the Fukuda definition at the first, and it has been
involved in testing different aspects of it, but it has not checked
if people with other diseases might also meet this new definition for
CFS. In most cases it doesn't have to - most are excluded from taking
part in CFS studies anyway.
Dr. Reeves' analysis did find that the empirical definition did
successfully differentiate CFS from CFS-like and healthy people -
something neither the Fukuda definition nor symptoms have been able
to do. Interestingly the three subjects in which the CFS patients did
not differ from the CFS-like population had a psychological or mental
basis; they were motivation, role emotional and mental health. The
empirical definition was able to target a group of CFS patients in
which a category called 'role physical' was, in contrast to the
CFS-like patients, strikingly important. This suggests the definition
did single out a distinct group of patients.
This is an ongoing battle to define CFS and it is a very important
one. If a new group of patients that differs from the type of CFS
patient now studied is selected for new studies, then their presence
will alter both the findings and direction of CFS research. Whether
or not these CFS-like patients are similar or not to 'CFS patients'
it is clear that there are a lot more CFS-like than 'CFS' patients
out there; this year for a short period the CDC boosted their
estimates of CFS prevalence 4-fold to 4 million.
Two things at least are clear; the CFS research community needs to a)
come up with a good definition and b) the entire research community
needs to use it. No matter how good a definition is, if it is not
used by the majority of the CFS research community, then its
introduction will only further muddy the waters.
Toward a (Real?) Empirical Definition of CFS?
Leonard Jason, Karina Corradi, Susan Torres-Harding. Toward an
empirical case definition of CFS. (Poster)
Whether or not the new CDC empirical definition needs to be changed,
Dr. Jason is bringing up questions that need to be asked. In this
study he outlines an empirical way to come up with an empirical definition.
In this study he gave 114 CFS patients questionnaires regarding
symptoms associated with a range of different systems including the
vascular, inflammatory, muscle/joints and others. If I understand
this correctly he found that using these symptoms provided a better
biological interpretation than did using those associated with the
Fukuda definition. He was able to identify four clusters of patients
(subsets) with distinct symptom presentations. He noted two of the
clusters identified could not have been assessed using the Fukuda
definition. This means that a much broader range of symptoms need to
be assessed in CFS than the seven or eight present in the Fukuda
definition and that important symptoms in CFS have been missed.
This study leapfrogged over the question of how to define CFS in
general and went to what may be an even more important question;
Identifying coherent subsets in CFS. We often think of a biomarker as
a kind of holy grail in CFS research but defining coherent subsets
would, if anything, have even more importance. Being able to do would
constitute an evolutionary leap in our understanding of CFS, lead to
more significant and replicable study findings and initiate the
breakup of the CFS label. Given the worries about the vague CFS
definition and the subsets, it is unfortunate that it took 15 years
to get this type of study accomplished.
To its credit the CDC has already looked at that question of symptom
presentation in CFS and CFS-like patients; they found that, even
using an expanded symptom list, the two groups looked very similar
symptomatically and they could not differentiate them. They, of
course, also attempted to derive subsets using the voluminous data
set generated by the Wichita studies.
We end this section with a question asked by Mary Schweitzer at the
conference that bears on this issue, "How do we get homogenous sample
groups for CFS studies?"
Dr. De Meirleir stated that the current definition was created before
researchers had any idea of possible biomarkers in CFS. He thought
the definitions will hold for only a few more years. Once researchers
identify the different mechanisms present in CFS, the present
definitions will fade away.
Steven Du Pre
Poetry website: http://www.angelfire.com/poetry/soareagle/index.html
"By words the mind is winged." Aristophanes
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