Problems in defining post-exertional malaise (Jason et al., 2015)

Dolphin · Nov 28, 2018

From 2015 but I only read it recently:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4295644/

J Prev Interv Community. 2015;43(1):20-31. doi: 10.1080/10852352.2014.973239.
Problems in defining post-exertional malaise.
Jason LA1, Evans M, So S, Scott J, Brown A.
Author information

Abstract
Post-exertional malaise (PEM) is a cardinal symptom of the illnesses referred to as Myalgic Encephalomyelitis (ME), Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS), and chronic fatigue syndrome (CFS).

PEM is reported to occur in many of these patients, and with several criteria (e.g., ME and ME/CFS), this symptom is mandatory (Carruthers et al., 2003 , 2011 ).

In the present study, 32 participants diagnosed with CFS (Fukuda et al., 1994 ) were examined on their responses to self-report items that were developed to capture the characteristics and patterns of PEM.

As shown in the results, the slight differences in wording for various items may affect whether one is determined to have PEM according to currently used self-report criteria to assess CFS.

Better understanding of how this symptom is assessed might help improve the diagnostic reliability and validity of ME, ME/CFS, and CFS.

KEYWORDS:
Myalgic Encephalomyelitis; Myalgic Encephalomyelitis/chronic fatigue syndrome; chronic fatigue syndrome; post-exertional malaise
PMID: 25584525
PMCID: PMC4295644

DOI: 10.1080/10852352.2014.973239
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Dolphin · Nov 19, 2018

Jason, King, and colleagues (1999) found that in a group of individuals with CFS, the number of individuals endorsing PEM ranged from 40.6-93.8% depending on how the question was assessing this symptom. This lack of uniformity in the way PEM is measured represents a significant problem for the scientific community. Due to vague wording, some individuals with ME/CFS, ME and CFS might not be identified as having PEM when they may actually be experiencing it.
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Jason LA, King CP, Richman JA, Taylor RR, Torres SR, Song S. US case definition of chronic fatigue syndrome: Diagnostic and theoretical issues. Journal of Chronic Fatigue Syndrome. 1999; 5:3–33. doi: 10.1300/J092v05n03_02.

Dolphin · Nov 19, 2018

However, none of these eight indicated that they felt worse than usual for 24 hours or more after exercise. This indicates that a primary reason that these eight did not get counted as having a PEM symptom involved the issue of having less than 24 hours of feeling worse after exertion. We also asked two follow-up questions involving more details about the duration and onset of fatigue: ‘How long does the fatigue last after physical or mental exertion?’ and ‘How long does it take the fatigue to begin after physical or mental exertion?’ Five individuals indicated that their fatigue lasted less than 24 hours after physical or mental exertion. Only one individual specified fatigue that lasted exactly 24 hours and two participants indicated that they experience ‘more than three hours’ of fatigue with no time frame specified. Additionally, variations in onset of fatigue were found among these eight individuals. Three participants reported fatigue that is elicited ‘immediately,’ but the others all reported a delayed onset. For two participants, it took ‘about one hour,’ for two others, it took ‘from one to three hours,’ and for one participant, it took ‘more than three hours.’

It is possible that the term “exercise” was a critical word that differentiated those meeting Fukuda criteria for PEM versus not having PEM. To assess this, we asked participants’ level of agreement to the following statement: ‘Exercise brings on my fatigue.’ Aside from one participant who ‘strongly agreed’ that exercise brings on fatigue, most of these participants (five) did not agree with this item. Additionally, one participant was unsure, and one did not respond to this item. This suggests that fatigue among these eight participants was not caused by physical exercise as these individuals may not engage in exercise at all or it might be that mental exertion or other types of activity rather than exercise brings on their PEM.
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Dolphin · Nov 19, 2018

We therefore asked these eight participants two additional items about symptoms that did not explicitly involve exercise but rather physical activity. Only two participants had ‘moderate or frequent symptoms’ of prolonged fatigue after physical activity. However, when asked about excessive muscle fatigue with minor activity, four participants indicated that they have ‘moderate or frequent symptoms,’ and one participant indicated ‘severe or very frequent symptoms.’ Evidently, referring to minor activity or physical activity might make a difference as does exercise versus excessive muscle fatigue.
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In addition to the self-report items, the primary diagnosing physician’s notes were examined to see whether there was any additional information provided about PEM among these eight participants. Four of the participants were noted to have PEM symptoms during the medical interview. For another participant, it was noted that this individual “does not exercise much anymore.” Thus, because this individual had reduced levels of activity, it was unclear whether exercise would actually elicit PEM. It is uncertain from the medical notes whether or not the others might have had PEM, but at least 50% of the eight participants had this critical symptom based on these medical notes.
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These 8 had answered no to the following question:

Fukuda et al. (1994) question: ‘Do you feel generally worse than usual or fatigued for 24 hours or more after you have exercised?’
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Dolphin · Nov 19, 2018

Secondly, if participants have fatigue that is present for more than 50% of the time, fatigue that may arise after exercise might not make them feel any more fatigued than usual.
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Dolphin · Nov 19, 2018

However, none of these eight indicated that they felt worse than usual for 24 hours or more after exercise. This indicates that a primary reason that these eight did not get counted as having a PEM symptom involved the issue of having less than 24 hours of feeling worse after exertion. We also asked two follow-up questions involving more details about the duration and onset of fatigue: ‘How long does the fatigue last after physical or mental exertion?’ and ‘How long does it take the fatigue to begin after physical or mental exertion?’ Five individuals indicated that their fatigue lasted less than 24 hours after physical or mental exertion. Only one individual specified fatigue that lasted exactly 24 hours and two participants indicated that they experience ‘more than three hours’ of fatigue with no time frame specified. Additionally, variations in onset of fatigue were found among these eight individuals. Three participants reported fatigue that is elicited ‘immediately,’ but the others all reported a delayed onset. For two participants, it took ‘about one hour,’ for two others, it took ‘from one to three hours,’ and for one participant, it took ‘more than three hours.’
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Dolphin · Nov 19, 2018

While some items in our study specified the type of activity causing fatigue, only one question explicitly asked about muscle fatigue instead of using ‘fatigue’ in general. Because fatigue can be experienced by everyone, when measuring PEM, using the general term fatigue will not accurately differentiate patients from healthy controls. Therefore it is critical when using self-report surveys to contain questions that ask about both the ill-feelings of fatigue and the physical loss of muscle strength after mental or physical activity. By doing so, specific characteristics of PEM can be better identified with patients. Thus, as shown in the results of the current study, the word ‘fatigue’ is complex and means different things to different people, and items that use this term often do not capture the symptoms of PEM among patients.
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Dolphin · Nov 19, 2018

Some individuals may experience PEM for 24 hours or longer, whereas others may only experience it for one hour. Some individuals experience PEM immediately after mental or physical exertion, but others develop PEM hours after the initial activity of cause.
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A study published this year i.e. subsequent to this paper, is a good example to cite to make this point.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197811

PLoS One. 2018 Jun 1;13(6):e0197811. doi: 10.1371/journal.pone.0197811. eCollection 2018.
Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey.
Chu L1, Valencia IJ1, Garvert DW1, Montoya JG1.
Author information

Abstract
BACKGROUND:
Post-exertional malaise (PEM) is considered to be the hallmark characteristic of myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS). Yet, patients have rarely been asked in formal studies to describe their experience of PEM.

OBJECTIVES:
To describe symptoms associated with and the time course of PEM.

METHODS:
One hundred and fifty subjects, diagnosed via the 1994 Fukuda CFS criteria, completed a survey concerning 11 symptoms they could experience after exposure to two different types of triggers. We also inquired about onset and duration of PEM and included space for subjects to write in any additional symptoms. Results were summarized with descriptive statistics; McNemar's, paired t-, Fisher's exact and chi-square goodness-of-fit tests were used to assess for statistical significance.

RESULTS:
One hundred and twenty-nine subjects (90%) experienced PEM with both physical and cognitive exertion and emotional distress. Almost all were affected by exertion but 14 (10%) reported no effect with emotion. Fatigue was the most commonly exacerbated symptom but cognitive difficulties, sleep disturbances, headaches, muscle pain, and flu-like feelings were cited by over 30% of subjects. Sixty percent of subjects experienced at least one inflammatory/ immune-related symptom. Subjects also cited gastrointestinal, orthostatic, mood-related, neurologic and other symptoms. Exertion precipitated significantly more symptoms than emotional distress (7±2.8 vs. 5±3.3 symptoms (median, standard deviation), p<0.001). Onset and duration of PEM varied for most subjects. However, 11% reported a consistent post-trigger delay of at least 24 hours before onset and 84% endure PEM for 24 hours or more.

CONCLUSIONS:
This study provides exact symptom and time patterns for PEM that is generated in the course of patients' lives. PEM involves exacerbation of multiple, atypical symptoms, is occasionally delayed, and persists for extended periods. Highlighting these characteristics may improve diagnosis of ME/CFS. Incorporating them into the design of future research will accelerate our understanding of ME/CFS.

PMID:

29856774

PMCID:

PMC5983853

DOI:

10.1371/journal.pone.0197811
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Hence, it would be more effective for self-report items to have scales that contain a wider set of time frames rather than solely ‘24 hours or longer.’
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Dr Carrot · Nov 19, 2018

129 participants, self-reported outcomes. Feels like the S4ME membership could do something equal or even better, with better questions and a larger sample size.

Dolphin · Nov 19, 2018

It contains some criticisms of the ME-ICC criteria:

Recently, a new case definition for ME has been introduced by the Myalgic Encephalopmyelitis International Consensus Panel (ME-ICC) (2012). Within their primer, PEM is referred to as post-exertional neuroimmune exhaustion (PENE). The authors indicate that PENE can be assessed with a two consecutive day exercise test involving expired gas exchange, but as indicated above, cardiopulmonary devices are expensive and not always available in clinic and research settings, so self-report questionnaires will need to be used in most settings to assess this symptom cluster. For the self-report questionnaire that is included in the primer, PENE is characterized by 1) marked, rapid physical or cognitive fatigability in response to exertion, 2) symptoms that worsen with exertion, 3) post-exertional exhaustion that may be immediate or delayed, 4) exhaustion is not relieved by rest, and 5) substantial reduction in pre-illness activity level due to low threshold physical and mental fatigability. There are a number of problems with this level of specification. First, it is unclear whether all five characteristics must be present for PENE to occur. If a person meets all but one characteristic, it is unclear whether they would be counted as having this symptom. For example, in a separate dataset utilized by Jason, Sunnquist, Brown, & Evans (2013), it was found that out of 122 participants who met the Canadian ME criteria (Carruthers, 2011), only 77 participants would have met five differently worded statements that are characteristics of PENE. Therefore, whether all characteristics or just some are required for the ME-ICC case definition of PENE is of considerable importance.

Furthermore, the precise operationalization of each of these characteristics is still ambiguous. For example, the requirements for the onset and duration of PENE are vague and therefore reliability problems might occur. Additionally, physical and mental fatigability is supposed to result in a substantial reduction in activity level that can be mild, moderate, severe, or very severe. However, the meaning of substantial reduction or significantly reduced activity level is not clearly defined. As an example, one characteristic of PENE involves having a “Low threshold of physical and mental fatigability (lack of stamina) results in a substantial (approximately 50%) reduction in pre-illness activity level.” Directions are then provided in the primer indicating that symptom severity must result in a significant reduction in a patient’s premorbid status, which can be rated as mild, moderate or severe. Moderate is defined as an approximate 50% reduction in pre-illness activity level, but there is also an option for mild, which “meets criteria” and involves a significant reduction; but as moderate is defined as a 50% reduction, mild must be less, and this contradicts the prior statement regarding the need to have a 50% reduction. Similar issues arise with the other required symptoms, thus, there will likely be reliability problems with this new case definition.
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2011 International Consensus Criteria paper:

Operational notes: For a diagnosis of ME, symptom severity must result in a significant reduction of a patient’s premorbid activity level. Mild (an approximate 50% reduction in pre-illness activity level), moderate (mostly housebound), severe (mostly bedridden) or very severe (totally bedridden and need help with basic functions). There may bemarked fluctuation of symptom severity and hierarchy from day to day or hour to hour. Consider activity, context and interactive effects. Recovery time: e.g. Regardless of a patient’s recovery time from reading for ½ hour, it will take much longer to recover from grocery shopping for ½ hour and even longer if repeated the next day – if able. Those who rest before an activity or have adjusted their activity level to their limited energy may have shorter recovery periods than those who do not pace their activities adequately. Impact: e.g. An outstanding athlete could have a 50% reduction in his ⁄ her pre-illness activity level and is still more active than a sedentary person.
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3 Symptom severity impact must result in a 50% or greater reduction in a patient’s premorbid activity level for a diagnosis of ME. Mild: approximately 50% reduction in activity, moderate:mostly housebound, severe: mostly bedbound and very severe: bedbound and dependent on help for physical functions.
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2012 International Consensus Primer:

Operational Notes: For a diagnosis of ME, symptom severity must result in a significant reduction of a patient’s premorbid activity level. Mild (meet criteria, significantly reduced activity level), Moderate (an approximate 50% reduction in pre-illness activity level), severe (mostly housebound), or very severe (mostly bedridden and needs help with basic functions). There may be marked fluctuation of symptom severity and hierarchy from day to day or hour to hour. Consider activity, context and interactive effects. Recovery time: e.g. Regardless of a patient’s recovery time from reading for ½ hour, it will take much longer to recover from grocery shopping for ½ hour and even longer if repeated the next day – if able. Those who rest before an activity or have adjusted their activity level to their limited energy may have shorter recovery periods than those who do not pace their activities adequately. Impact: e.g. An outstanding athlete could have a 50% reduction in his/her pre-illness activity level and still be more active than a sedentary person.
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