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Prof. Jason:


(post-exertional malaise)

en het belang daarvan

voor de definitie

van ME (en CVS)






In een bijdrage voor CAA, To PEM or not to PEM? That is the question for case definition,

gaat prof. Jason dieper in op het verschijnsel post-exertional malaise (verergering van klachten/verlies van spierkracht na inspanning, en het belang daarvan voor de definitie.


Prof. Jason gaat in op de geschiedenis (van ME via CVS-1, CVS-2 terug naar ME/CVS en ME)

en op het vaststellen van post-exertional malaise (objectief: fietstesten, en subjectief: vragen).


Ik ben het oneens met prof. Jason als hij stelt dat het vaststellen van post-exertional malaise nooit zonder zelfrapportage van de patiŽnt (subjectieve vaststelling) zou kunnen.

Zolang deze klacht (deels) subjectief vastgesteld wordt, zullen discussies voortduren.

Het objectief vaststellen van de effecten van inspanning (via genexpressie, of de objectieve prestatie een tweede fietstest et cetera) is de enige manier om "ongelovigen"  te overtuigen.




Kommentaar van ondergetekende op het artikel (zie de CAA-website):



Oxidative stress is just one of the many abnormalities

induced/intensified by (mental and physical) exertion

that could account for PEM.


As substantiated in Twisk and Maes (2009):


Exertion induces post-exertional malaise

with a decreased physical performance/aerobic capacity, increased muscoskeletal pain, neurocognitive impairment, "fatigue", and weakness, and a long lasting "recovery" time.


This can be explained by findings that exertion may amplify pre-existing

pathophysiological abnormalities underpinning ME/CFS,

such as inflammation, immune dysfunction, oxidative and nitrosative stress,

channelopathy, defective stress response mechanisms and

a hypoactive hypothalamic-pituitary-adrenal (HPA) axis.


Using Fukuda et al. (1994) criteria and

PEM, "fatigue", and a subjective feeling of infection as discriminatory symptoms

we recently established that


ME, "CFS" (Fukuda/not-ME) and CF are distinct diagnostic categories.

ME patients have significantly higher scores on

concentration difficulties and a subjective experience of infection, and

higher levels of IL-1, TNFα, and neopterin than patients with "CFS".


Myalgic Encephalomyelitis (ME), Chronic Fatigue Syndrome (CFS),

and Chronic Fatigue (CF) are distinguished accurately:

Results of supervised learning techniques applied on clinical and inflammatory data.

Psychiatry Res. 2012 Apr 20. doi: 10.1016/j.psychres.2012.03.031.

Maes M, Twisk FNM, Johnson C.


It is time to leave the CFS label and "fatigue" behind us and

to make a clear distinction between

ME patients (those with PEM and e.g. cognitive impairment) and

"CFS" patients (those without PEM).







To PEM or not to PEM? That is the question for case definition


By Leonard A. Jason, Ph.D. and Meredyth Evans, DePaul University



The criteria for defining cases is an important topic in research and medicine. For chronic fatigue syndrome, it has been a vexing topic whether one considers CFS to be a new condition identified with the 1988 case definition (Holmes, et al.) or a new (if unwanted) name for a condition that has existed for decades, if not centuries, by other names. Here we will examine the cluster of symptoms known as post-exertional malaise (PEM) and its importance in defining the condition. PEM is also known as post-exertional relapse. It refers to the aggravation of various symptoms following even modest physical or mental exertion.







It is important to note that PEM cannot be definitively established without the inclusion of the patients' self-reported symptoms. Thus, there is a need to develop self-report methods for capturing the frequency, severity and duration of this cardinal symptom. Jason and colleagues (1999) found that in a group of individuals with ME/CFS, PEM ranged from 40.6-93.8% depending on how the question of this symptom was asked. This lack of uniformity in the way PEM is measured represents a significant problem for the scientific community studying this illness.




Our research group feels that that post-exertional malaise is a cardinal feature of ME;

the definition recognizes post-exertional malaise as

prolonged restoration of muscle power following either mental or physical exertion.