This section is the one I am most concerned about.
I am sorry this is rather muddled due to my exhaustion and rather blunt. I don't feel understood by the dePaul group. More importantly, I think the dePaul questionnaires are so flawed as to be harmful to pwME and really want your team to understand the misunderstanding of PEM you are perpetuating.
I
Question 21 of 43
You will now be presented with a series of Post-Exertional Malaise case definitions. For each one please rate how often (frequency) and how intensely (severity) you have experienced this symptom over the past 6 months.
For each, you are asked these 2 questions:
0
None of the time
1
A little of the time
2
About half the time
3
Most of the time
4
All of the time
0
Not present
1
Mild
2
Moderate
3
Severe
4
Very severe
Symptoms for which you are asked to answer the above 2 questions:
Next day soreness or fatigue after non-strenuous, everyday activities
Mentally tired after the slightest effort
Physically drained or sick after mild activity
Dead, heavy feeling after starting to exercise
You can interpret the word exercise as any daily activity you do such as even walking around in your house.
Minimum exercise makes you physically tired
You can interpret the word exercise as any daily activity you do such as even walking around in your house.
None of these describe PEM from my decades of experience living with ME/CFS through severity levels from mild to severe, as a carer for my daughter who has had severe ME/CFS for decades, and through the last decade daily study of research and interacting with pwME of all severity levels and our collective reading and studying and discussions of PEM. Nor do they fit with the definitions you yourselves have given. They describe fatigablity.
I said this in my first attempt at a comment:
You describe each of the statements asked about as 'a series of PEM case definiitions'. They are no such thing, at least not in any definition I've seen, or in my experience. They are descriptions of fatigability which for many if not all pwME is part of what ME/CFS is. I experience all of them all the time during and after every activity.
I have now looked up the term 'case definition', and see, according to wikipedia, that it is a term used in epidemiology to gather population statistics either in outbreaks of illness or for prevalence studies of any illness. It may be different from diagnostic criteria used for diagnosing individuals as part of their medical care.
https://en.wikipedia.org/wiki/Clinical_case_definition#:~:text=In epidemiology, a clinical case,e.g., incidence and prevalence).
Important characteristics of case definitions are, depending on purpose, focus on specificity or sensitivity or both.
Checking the definitions
Sensitivity and specificity are two measures of a test's accuracy, particularly in medical diagnostics. Sensitivity measures how well a test identifies those who have the disease (true positives), while specificity measures how well it identifies those who do not have the disease (true negatives). A high sensitivity test has few false negatives, and a high specificity test has few false positives.
The list you give are all about physical and mental fatiguablity, not about PEM. Worse still, they are likely to be answered in the affirmative by someone recovering from an infection, someone deconditioned, some with insomnia and other sleep problems like sleep apnoea, someone who is depressed, and a wide range of other fatiguing conditions.
It seems to me to fail spectacularly on specificity.
And pwME are likely to answer yes to all of them as present all the time, so it doesn't identify the episodic nature of PEM crashes for pwME. Delayed onset muscle soreness is not PEM, though it may be part of it, delayed onset post exertional fatigue is not PEM, though likely to be part of it, fatiguablity is not PEM and likely to occur every day in ME/CFS, not just in PEM.
Because pwME experience both fatigability and PEM, your list of fatigablity will likely pick up pwME, so will appear to be identifying people with PEM, but they don't define PEM, they define another aspect of ME/CFS. So it may appear to have high sensitivity, even though it's not asking directly about PEM, but about another aspect of ME/CFS in people who also have PEM.
So doesn't that mean they fail on sensitivity. They are not picking up features of PEM but of fatigabilty, PEF, DOMS, etc.
Why not use the set of key features of PEM as in our fact sheet, or something similar that identifies features more specific to PEM?
In your reply to me you did not address this concern, instead you ignored the fact sheet I linked which gave a clear description of my understanding of the key features of PEM. You focused instead on pulling apart one sentence in my response that was not intended as a definiton, but was trying to point to a problem I saw in your first abbreviated version of a PEM definition which as you pointed out, you yourselves wrote differently in two contexts in the survey.
Your reply completely misses my point:
But your major issue is contained in this paragraph: “I think the problem I and others are having with this questionnaire is a fundamental difference in understanding the phenomenon of PEM. You define it as: ‘”‘PEM involves a worsening of symptoms after physical, cognitive, or emotional exertion.’”
In our consent form, we defined PEM in this way, but it was an abbreviated version of our conception of ME/CFS. There are many questionnaires/surveys that do use this type of definition to define PEM. However, in our actual survey, we did provide what we considered our definition of PEM, and it is what we expected patients to refer to when answering our questions. At the start of our survey, in Question 1, we provide responders with our definition of PEM. “Over the past 6 months, have you experienced post-exertional malaise, which is defined as an abnormal response to minimal amounts of physical and/or cognitive exertion, with symptom severity and duration out of proportion to the initial trigger?” From our data of people with ME, 99.6% answered affirmatively to this statement, suggesting that our phrasing has high sensitivity.
So, to repeat, at the beginning of our survey, we are defining PEM as “an abnormal response to minimal amounts of physical and/or cognitive exertion, with symptom severity and duration out of proportion to the initial trigger.” In contrast, in your post, you defined PEM as “the usually delayed much worse episodes we experience when we have done a bit more exertion than usual, that is usually delayed after the triggering exertion and that usually lasts for days or much longer before the episode eases.”
These two definitions are worth examining in more detail as they are a major reason that we have differences in opinions on our definitions of PEM. There are two parts of this difference, and to summarize, you use the term “much worse episodes we experience” and “a bit more exertion than usual” whereas our group uses the terms: “an abnormal response to minimal amounts of physical and/or cognitive exertion” which is “out of proportion to the initial trigger.” So, one defines the trigger and the other defines the PEM outcome, and we will inspect both aspects of our different approaches to these issues. Regarding PEM outcome, you prefer “much worse episode” and we use the term “abnormal response”, and both try to capture the phenomena. In your PEM definition, you use the term “much worse episodes” to differentiates the current symptoms from what have been experienced previously. We have some concerns with these types of phrases using terms such as worse in a comparison capacity. The use of words such as “much worse” reminds us of the controversy regarding Chalder et al.’s (1993) fatigue scale, whose responses were rated on a four-option continuum ranging from 0 = less/better than usual to 3 = much more/much worse than usual. For patients that have been sick for many years, unfortunately, it is unclear what it means to have symptoms that are “worse than usual”. The Chalder Fatigue Scale has not demonstrated efficacy in discriminating between different subtypes of individuals with fatigue, and it has not demonstrated an ability to distinguish individuals with ME/CFS from those with primary depression (Friedberg & Jason, 1998). We might mention that the Chalder group and their scales were used by the British investigators who popularized CBT for patients with ME/CFS.
Now we examine the differences in the trigger phrases for our definitions of PEM. Our group would argue that there are some benefits of our PEM definition of “an abnormal response” to exertion that is out of proportion to the trigger, which is a marker that would signify to the patient that a PEM experience has occurred. In other words, you define the trigger as “a bit more exertion than usual” whereas we define it as “minimal amounts of physical and/or cognitive exertion with symptom severity and duration out of proportion to the initial trigger”. One could debate which is more accurate. In the article by Holtzman et al. (2019), when describing PEM triggers, 78.2% endorsed “basic activities of daily living”, 64.5% endorsed “positional changes”, and 93.2% endorsed “emotional stress (good or bad)”. Additionally, 84.9% said there were some instances in which the specific precipitants could not be identified.” So, there will be times when PEM occurs where it is unclear what your “a bit more exertion than usual” would refer to. In other words, it could be argued that some patients might not be clear with what you refer to as “a bit more exertion than usual”. If severely affected, it might not be clear what is more than usual. For example, it might not be more exertion that precipitates PEM but usual amounts of exertion in addition to other triggering events, such as positional changes. This gets into the complexity of defining PEM. If bedbound, and if PEM occurred with no exertion, but some other triggering event such as bright light, would such a person also not have PEM according to your definition. What if the person’s baseline symptoms are so intense that “more than usual” is no longer something the person can understand and would such a person also be excluded as not being able to have PEM. I am just suggesting that what is “usual” is not an easy concept to understand for a person who has lost that ability to have what is called a “usual” baseline. So, when we refer to symptom and duration out of proportion to the trigger, our phrasing trigger might be more flexible and accurate than your use definition which uses the term “usual”.
Finally, by your definition stating that the duration of PEM usually lasts for days or longer, there might be unintentional, but scientific bias introduced to a survey trying to assess PEM. For many patients, the PEM does not last for days or longer and in our database, we did identify those whose PEM occurred for 24 or less hours. It could be that for some, pacing and carefully observing their activity could limit PEM to less than 24 hours. In contract, our definition of “duration out of proportion to the initial trigger” does not define the period of time, and that way a respondent is not given an expectation of how long the PEM should last, which if stated and defined as you have could even unintentionally bias the results of an investigation by suggesting to the respondent of how long PEM might last.
I am struggling to read through such a long reply based on a misreading of my post, where I was not defining PEM, I was trying to point out things I saw as missing in your first abbreviated definition. What has Chalder's ridiculous questionnaire to do with it?
I feel like you are trying to put me down and score points, not to understand what I am getting it. If you had bothered to read our PEM fact sheet as I asked you to, you would know that we use terms like an abnormal response to minimal amounts of exertion and included all the points in your definition. Please don't assume you are dealing with someone ignorant. I wrote the PEM factsheet with the help of forum members over a couple of months earlier this year. I have read the research on PEM, such as it is, I have studied the definitions and diagnostic criteria, I am not as ignorant as your answer assumes.
I suspect you have given up reading my comments now. I am struggling with severe difficulty typing and even seeing clearly after all this effort, so I may not be as clear as you would like, but I do want to convey to you how damaging it is to use a PEM set of 'case definitions' that are so poor on specificity and sensitivity that you misleading sick people, clinicians and badly affecting research, leading, as @Nighsong so clearly showed, to perpetuation of dreadful psychobehavioural research.
Finally if you are still reading, if I wanted to design a questionnaire to find out whether someone experienced PEM, I would
1. Define PEM clearly as in our key features and ask yes or no to whether someone experiences each key feature
2. Ask a limited set of subquestions for each feature eg
- how long the most recent PEM episode lasted,
- whether they identified a trigger from a few broad categories including 'other',
- whether there was an identifiable delay between trigger and PEM onset, and how long,
- and a basic list of core symptoms, which symptoms they have all the time, which worsen during PEM, and which symptoms only occur during PEM episodes. Allow a category of 'other daily symptoms' and of 'other PEM only symptoms'.
- for severity of functional loss during PEM, Use a severity scale such as Bell, NICE or MEA to and ask to identify their usual severity and their severity during PEM episodes
3. Ask a question to distinguish between PEM and PEF/DOMS/exercise intolerance, eg which of these best describes the effect of physical activity...
