Saturday, July 12, 2014

Measuring Post-Exertional Malaise

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CFS Central

Monday, July 7, 2014

CDC's head of CFS research Dr. Beth Unger said
at last month's Chronic Fatigue Syndrome
Advisory Committee meeting
( that she couldn't figure
out how to measure post-exertional malaise
(PEM) - the hallmark of ME -and thus believes
problems would ensue if PEM is a mandatory

        "My concern about making
        post-exertional malaise an absolute
        criteria for diagnosis is if you don't
        have a consistent, validated way of
        measuring it that clinicians can use
        easily, it's big barrier,"

Unger explained at the meeting.

A few minutes later, when committee member
Donna Pearson asked again about PEM being
included in the criteria, Unger replied:

        "I think everybody agrees that it's
        very characteristic and a very
        important symptom, and clinicians will
        tell you that they can recognize it, they
        can illicit this information from
        patients, but to make that quantifiable
        and to make it easily implementable is
        another question...."


Several researchers have
shown how to measure PEM.

Cardiac pulmonary testing used by Dr. Chris
Snell is one way, gene expression testing
devised by Drs. Alan and Kathleen Light is
another, comprehensive patient history is yet
another, and using a pedometer like the Fitbit
would also work.

Dr. Jose Montoya conducted VO2 max studies
( with patients on the
antiviral Valcyte to determine if their exercise
tolerance improved on the antiviral.

Unger's familiar with all of this.

In fact, Unger is one of the authors of a 2012
paper: "Minimum data elements for research
reports on CFS" ( in which
the authors discuss how to measure PEM:

"As post-exertional malaise is a key symptom of
all CFS case definitions, it would be appropriate
to measure the extent of activity and how such
activity might result in symptoms of fatigue and

Light et al. (2009) found patients with CFS
demonstrated increases after exercise that
reliably exceeded responses of control subjects
in mRNA for genes receptors that can detect
muscle produced metabolites, genes that are
essential for sympathetic nervous system
processes, and immune function genes.

The researchers concluded that CFS patients
might have enhanced sensory signal for fatigue
that is increased after exercise.

Activity, or in work performed is generally
quantified in terms of energy used, i.e., caloric

Because this is difficult to measure during
activity, total oxygen consumption which
increases in a similar fashion, is typically used
in its place.

"Sometimes represented as METs or metabolic
equivalents, oxygen consumption may be
assessed directly using cardiopulmonary
exercise testing with measured gas exchange
(Milani et al., 2006), or estimated from heart
rate or other indicators of effort such as time
and/or distance travelled.

Assessment of effort is critical when exercise is
used as a physiological stressor to elicit
symptoms in CFS patients or for assessments
of functional capacity as part of clinical trials.

Heart rate as a percentage of age-predicted
maximum is the most recognized indicator of
subject effort for both maximal and submaximal
exercise protocols.

However, the maximal heart rate response to
exercise varies widely in the general population
(Balady et al., 2010) and has been shown to be
blunted in some subjects with CFS (e.g.,
VanNess et al., 2003) and also in fibromyalgia
(Ribeiro et al., 2011).

"As an alternative to heart rate, the peak
respiratory exchange ratio (RER) is
acknowledged as the most valid and reliable
gauge of subject effort (Balady et al., 2010).

Because it can only be obtained from
ventilatory expired gas analysis, RER may not
be available in all exercise studies.

Similarly, submaximal exercise protocols do not
provide for the measurement of peak RER.

In such instances selecting alternative
measures that can accurately assess effort
both within and across subjects is particularly

In addition, in Table 2 in the paper, the authors
cite actigraphy ( and
pedometers for activity assessments.

        Thus, Unger knows how to measure

        So why is CDC trying to bury PEM?

After all, PEM is the most important symptom of
the disease - and PEM distinguishes ME patients
from people diagnosed with CFS who in reality
are just depressed.

But maybe that's the point:

To lump bona fide ME patients in with the

That way you don't get meaningful data or
treatment, and the band plays on.

Every time I think CDC can't get more
devious, the agency surprises me.

First, Unger nixed a two-day exercise test
( in favor of a one-day
test, even though Dr. Chris Snell has shown PEM
isn't apparent under the second day of testing.

And now Unger can't figure how to measure

If Unger is hung up a "consistent, validated way"
of measuring PEM, she only has herself to blame
for not having done a two-day exercise test
after all these years.

         Leaving off PEM in the definition is like
        omitting elevated blood sugar in
        diabetes or a depressed CD4 count in

It's insanity.

*HHS's mission is to redefine ME/CFS with yet
another broad, erroneous case definition, which
will include countless people who do not have
ME/CFS, so they can recommend CBT, GET, and
anti-depressants, and so they can bury the
scientific, biomedical evidence of ME/CFS*.

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