A brief, comprehensive measure of post-exertional malaise, 2025, Jason and Chee

[poetinsf]

Defining post-exertional malaise "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" may not be enough. Fatigue and other symptom response to exertion can be *predictably* out of proportion compared to healthy people even when not in PEM. At least that is my experience when I was in deeper end of ME/CFS. If I walked 1 km, for example, I could predict that I would spend a few more hours lying down the next day. But that was not PEM even though fatigue was out of proportion to the exertion; it was an expected fatigue from the exercise given my condition at the time. PEM was when I spent 3 days in bed because I walked the same distance 5% faster.

This could be what led some people to think that other conditions like COPD also feature PEM. They compare the outcome to healthy people and conclude that it is PEM because fatigue is out of proportion (i.e., exercise intolerance). But it would not be PEM if you define PEM as the response that is out of whack with what is expected for a given condition and the amount exertion. This is why I prefer to separate post-exercise fatigue (expected for the condition) from post-exertional sickness (much worse than expected).

I guess it might help reduce misdiagnosis if a good way could be found to isolate fatiguability from PEM?

Right on the money. Except that DSQ-2 as it stands does not do that because it considers the outcome by itself. They should define PEM as a large differential between the expected outcome given the condition and the actual outcome, rather than the outcome by itself.

edit: added "exercise intolerance"

 

[poetinsf]

A confusing point over and above the fact that more rapid fatiguability is different to PEM, is that this more rapid fatiguability of itself is likely to be a symptom of ME?

I think it's fair to consider rapid fatiguability a symptom of ME/CFS. But I don't think we need to conflate it with PEM. PEM is a rather distinct and abrupt phenomenon of bottom falling out when you do just a tad bit more than you should whereas rapid fatiguability is more linear.

Further when in PEM more rapid fatiguability becomes even more rapid, more pronounced, which in turn means that the circumstances which contribute to triggering PEM will also trigger PEM more readily.

Insofar as the rapid fatiguability is a symptom of ME/CFS, it would be no surprise that it gets worse in PEM which is worsening of symptoms?

 

[Mij]

Yesterday I walked to the store at around 12:30, I don't normally go out walking any distance during that time of day and I could barely walk, my gait was jittery and I felt as though my legs would give out on me after 10 minutes. This was not PEM.

Yet the evenings I have a smooth gait and can power-walk for one hour and feel good afterwards as long as I stay within my limits, and don't have anything planned the next day.

I don't understand why time of day makes such a big difference in my case.

 

[poetinsf]

I don't understand why time of day makes such a big difference in my case.

Maybe it's similar to seasonality? There could be more of whatever makes your ME/CFS worse in the afternoon. Or, less of whatever makes your ME/CFS better.

 

[Mij]

Possibly. I also don't feel the need to lie flat/down in the evening like I do during the day. I can be upright all evening without feeling unwell.

 

[Verity]

Yesterday I walked to the store at around 12:30, I don't normally go out walking any distance during that time of day and I could barely walk, my gait was jittery and I felt as though my legs would give out on me after 10 minutes. This was not PEM.

Yet the evenings I have a smooth gait and can power-walk for one hour and feel good afterwards as long as I stay within my limits, and don't have anything planned the next day.

I don't understand why time of day makes such a big difference in my case.

I have a similar experience! I often pace around at night and have the sense that I’d get in trouble if I did it during the day.

 

[ME/CFS Science Blog]

Thanks for the useful analysis, especially the comments by Trish.

I'm also a bit confused by the scoring system. What does it do or indicate? Assuming a higher score means a stronger indication of PEM, then there are a couple of issues.

Having more triggers would be a stronger indication of PEM. If people say that mold, cold and chemicals trigger PEM, is that a stronger indication that they have PEM than those who don't? I would say the opposite, it's almost an indication that people might be misinterpreting PEM as simply 'symptom worsening'.​

​

A longer symptom duration also gets a higher score, and 12% said that their PEM lasted more than 2 years. In my view, that isn't an indication of having PEM. Such a long duration makes it less likely to be PEM and more ambiguous if it isn't simply a deterioration of the illness regardless of exertion levels. With PEM there is usually a clear relationship to exertion levels; you get worse when you do too much, and not otherwise. If patients get worse for 2 years continuously, then it could still be PEM but is much less clear. So responses like these should probably also results in a lower instead of a higher score.​

​

You also get a higher score if pacing is less effective, which is also curious. If the worsening is related to exertion (doing too much), then doing less should be expected to be helpful. So if pacing doesn't help at all, there is again more ambiguity if the symptom worsening is indeed PEM and related to too high exertion levels. If one were to give PEM scores based on the effectiveness of pacing (wouldn't recommend), then it would make more sense to give a higher score if pacing is useful, rather than if it is ineffective.​

​

Given all these issues, I'm kind of hoping that I misunderstood what the score is all about.

 

[ME/CFS Science Blog]

I suspect that's not going to happen unless we do it, or initiate ithere.

Agree, and would be happy to collaborate on something like this.

As I see it we would have to make a list of PEM statements that reflect how patients understand the concept and are useful to detect ME/CFS.

We would then need to test these in ME/CFS patients and disease controls to check the sensitivity and specificity. If a statement is only agreed upon by a minority of ME/CFS patients for example, it might not be useful as a criterium. On the other hand, if it is agreed upon by many controls who don't have ME/CFS, then it is not very useful either.

It would be great if we could involve a researchers who has experience with questionnaire design. Perhaps Kristian Sommerfelt might be suitable, given that he did a good job with FUNCAP?

 

[Kitty]

It would be great if we could involve a researchers who has experience with questionnaire design.

We'd need to identify what it's for first.

First, is a questionnaire about PEM triggers and duration useful for diagnostic purposes, given that diagnosis only requires PEM to be present? It doesn't need a detailed analysis of it, and a recently ill person may not yet have enough lived experience of PEM to complete one.

When it comes to management, do people who've got enough experience to answer the questions need or want an instrument to measure how long their PEM lasts? If so, what aspects of management do they need it to address in order to help them?

We can only start designing a questionnaire once we've got that clear.

 

[Midnattsol]

I think the patient experience is a very important point. We learn to talk about our symptoms in different ways. And for us there is the additional issue of people being told wrong things from trusted sources such as healthcare providers.

 

[Hutan]

I recently had the opportunity to try to explain to my new GP what delayed PEM felt like for me. One question was if I had 'difficulty with decision making' in which I answered no, and went on to explain that I have an energy deficit/depletion that affects both my physically and cognition that causes my brain to shut down, and that I need to lie down and rest to recover for a few days. She understood that.

I think a good analogy for cognitive issues in PEM is decision-making during a significant infection such as the flu or glandular fever. A lot of people can remember what that is like. There are studies of cognition during acute illness - reaction times slow, the ability to focus and hold information in short term memory decreases. Actually I think that might be a good area for us to look into - in acute illness, what aspects of cognition change, what causes it? I think there are recent studies on the biological basis of that effect.

The analogy also gets across the temporary nature of the cognitive disability. Provided someone is able to have time between episodes of PEM, it is not that the person with ME/CFS is incapable of good decision-making.

 

[Hutan]

To me, working out if someone has PEM takes time. A 'brief measure' of PEM perhaps is not what is needed. (It might depend on your definition of PEM - my definition is closer to a crash, a pressing need to lie down and do nothing for hours, than the vaguer 'increased symptoms' concept.)

I think it is necessary to consider activity over a period of time, ideally an objective measure of activity. Physical activity is the most easily measured and probably suffices for most people. So, I'd want someone trying to work out if someone has PEM to consider the pattern of activity. Are there periods of greatly decreased activity that fairly reliably follow increased activity?

That probably needs to be done early in the disease. People learn to manage activity levels in order to avoid PEM. If they are able to, they will pace to reduce PEM frequency, and so the pattern of activity followed by much reduced activity may not be observable.

Once someone has spent time observing the pattern, I think answering a few brief questions can diagnose PEM.

 

[duncan]

I think a good analogy for cognitive issues in PEM is decision-making during a significant infection such as the flu or glandular fever

I think it's a fair comparison for many pwME, period.

The analogy also gets across the temporary nature of the cognitive disability.

I fear it only addresses the degree. Some pwME have cognitive disability 24/7. It takes on a darker and more grim hue in PEM.

Provided someone is able to have time between episodes of PEM, it is not that the person with ME/CFS is incapable of good decision-making.

True, it's merely less common and more difficult.

 

[forestglip]

I think a good analogy for cognitive issues in PEM is decision-making during a significant infection such as the flu or glandular fever.

Yes, the two ways I like to think I'd try to get someone to understand how it feels are: in the midst of an awful infection, or immediately after running the longest distance you've ever run. Not exactly the same, but just to illustrate that it's life on "hard mode".

Try to live your life normally, doing schoolwork, making work decisions, sitting up or standing for eight hours a day at work, while in the midst of either of these scenarios.

Sure, maybe if it's a day or two a person could push through. But it never ends.

 

[duncan]

I think a good analogy for cognitive issues in PEM is decision-making during a significant infection such as the flu or glandular fever.

Without fever, at least for most pwME. How do you convey that? Hangover-like?

It makes me wonder about immune tolerance, which we lightly touched upon when it was the subject of the Nobel prize earlier.

That's an entirely distinct rabbit hole.

 

[Bivox]

We'd need to identify what it's for first.

First, is a questionnaire about PEM triggers and duration useful for diagnostic purposes, given that diagnosis only requires PEM to be present? It doesn't need a detailed analysis of it, and a recently ill person may not yet have enough lived experience of PEM to complete one.

When it comes to management, do people who've got enough experience to answer the questions need or want an instrument to measure how long their PEM lasts? If so, what aspects of management do they need it to address in order to help them?

We can only start designing a questionnaire once we've got that clear.

Hi
First of all: I am so impressed with the reflected and precise way in which you communicate! So much to learn here. What Kitty says hear to me is right on. I work all the time with diagnosing and following up ME/CFS in children and adolescents. As a working pediatrician working a lot with ME/CFS I have to find out if they have PEM or not. What I have arrived at (learning from so many patients and parents) is to ask: "What happens if you do very much more than you usually do because you want to or have to? First, being physically very much more active?" I continue "What happens in the following day/ days? Do you feel better?" If they say yes, they don't have PEM. If they say they feel very bad and can do much less of any activity compared to before the activity they might have PEM. I then as the same question about social/ kognitive activities (use a bit different words- age dependent). If I get the same answer (i.e. much more symptoms and definite reduction in capacity for activity, then they have PEM. I then ask them to describe how they feel/ what symptoms they have in the period they can do much less than normal and feel bad. I ask what the maximum duration typically has been. They usually say > 1 week. BUT major point is it depends heavily upon how they regulate activities. Both motor and kognitive/social/sound-light exposure/ upright position etc depending on how severe their disease is. Then I chart their strategy for regulation of activities and who/what really decides their activity level. It should (in children and adolescents at least) almost always NOT be above what they themselves think. Often should be below that. Then I have very much info from FUNCAP regarding their functional capacity. FUNCAP55 at diagnosis and later as needed. If not FUNCAP27.

Summing up: Identify PEM. After that amount of time having PEM is just a measure of how well they pace. Not ME/CFS severity. For that we think FUNCAP is much more appropriate tool. Actually, we didn't arrive at the response scale of FUNCAP. That was just a VERY clear "demand" from the respondents with ME/CFS in the early (first!) round of FUNCAP development (see www.funcap.no).

Another quite different question is if you want to research PEM per se. Very important aspect of ME/CFS research. THEN you need much more detailed assessments of the symptoms when pwME/CFS have PEM, its main triggers, delay, onset, biomarkers ++. Different topic.

Keep it up. We read you..
We will get this!
Kristian Sommerfelt

In very severe ME/CFS it is a bit different. We tried (Trude Schei, Arild Angelsen and me) to have a score to assess severity (ADLS score). It was developed and published before FUNCAP and does not pose questions in the same way i.e.: "What happens if you...". It askes about frequency of basic activities and calculates a score based on how taxing the activities were assumed to be.

 

[Trish]

Thank you for joining us, @Bivox. I agree with all you say about assessing PEM. I wonder whether we could devise a PEM questionnaire if only to stop doctors wrongly diagnosing daily fatigability as PEM.
It could be very short, much as the questions you ask your patients, and have supplementary sections asking about frequency, duration, symptom changes, function changes which may be helpful in increasing the doctor and patients understanding of how sick someone is and how well they are able to manage their activity and environment to reduce PEM, and what support they need.

 

[Mij]

Summing up: Identify PEM. After that amount of time having PEM is just a measure of how well they pace. Not ME/CFS severity.

The symptom severity of delayed PEM for a mild/moderate patient is just as severe as severe patients, except that severe patients are more limited and may not recover from that episode while others do eventually depending on how much they exceeded their 'energy limit'

I've avoided delayed PEM for years from pacing.

 

[Utsikt]

Hei @Bivox - hyggelig å høre at du følger med her! Takk for arbeidet ditt for oss!

I seem to remember that you once mentioned (maybe at Digging Deeper?) that you always ask the children to answer first, without letting the parents talk. Is that correct?

And that children often know more about the symptoms than their parents, but that the parents often get their functional capacity more correct (children tend to overestimate how much they can do)?

In light of that, are there any adaptations for children specifically that might be necessary to make for a questionnaire that attempts to identify if PEM is present? Would the answers be less reliable if the child and parent fills it out together, compared to on their own?

 

[Mij]

The ME specialist I saw in 1992 never mentioned PEM, that term wasn't used back then. His advice was to "do nothing' even when your symptoms start improving. Not easy to do. We don't have a biomarker and there are no treatments. Some people improve and recover from PVFS while others don't.