Post-Exertional Malaise - a discussion including defining and measuring PEM

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Maybe she didn't deteriorate on the second CPET because the dose of exertion wasn't enough. If she has been pacing well and isn't severely ill that could be plausible in my experience.

Moving on to the topic of true ME. If we assume that the situation is one where Ramsay's disease is often confused with several other similar diseases, then it would actually be a good idea to study all of these diseases together in order to find similarities and differences. Knowing what disease can look like Ramsay's disease but is actually different at biological level would be useful for those with Ramsay's disease as well.

 

Great news that your daughter has improved on some measure. I hope her improvements continue and daily life starts to show changes for the better.
You have just illustrated the complexity of the condition . One test result , but seemingly little actual difference.
CPET is an indicator based on physical exercise, but physical exercise is not the sole arbitrator of PEM.

 

Like the others, I agree this doesn't necessarily indicate that your daughter no longer suffers PEM.

The CPET is taken on 2 consecutive days but my window for PEM has ranged from immediate to up to 3 days, especially for a one off activity rather than daily life. This is why I'm like a broken record every time I see the up to 48 hour window. It could possibly be longer than 3 days for someone else. We don't know for sure.

I don't know if the way my experience of PEM changes throughout the course of my illness reflects underlying severity, improved pacing (possibly enforced by severity), the fluctuating nature of the condition or something else.

 

What would you class as valid? What research would you accept as proof of abnormality that can be put to clinical use?

 

To be clinically useful you need a measure that is clearly above some threshold that you can regard as normal. Very often that is arbitrarily defined as two standard deviations above a mean on a test report but in practice there tend to be more specific thresholds based on experience with that specific test. So the threshold for serum rate is the crystallisation point, not two standard deviations. The threshold for blood pressure is that which is known to be associated with increased morbidity.

We don't have a well defined threshold for 2day CPET based on repeated studies in different centres that takes confounding factors into account.

We also want to have some convincing explanatory link between the test result and the relevant symptom. CPET results at day 2 may have some indirect relation to PEM but they do not provide any sort of direct explanation. The reason for saying that is that people with PEM feel awful regardless of whether or not they try to exercise. PEM is something that is there at rest, not just on repeat exercise. So whatever the CPET is measuring it is not the cause of the symptom, which was there prior to exertion. That might not matter if we had a well tested hypothesis linking the two. Without that there is no reason at all to doubt that PEM is there in someone who feels worse after exertion but whose 2nd day CPET is normal.

So in simple terms I think we want some measure that is outside a normal range and present at rest in someone with PEM symptoms at that point in time and absent when PEM is not there.

 

The usefulness of the CPET testing is mainly that the results for people with ME are different from healthy people so it shows that there is something biological going on.

The actual results indicate that something is wrong with aerobic respiration which indicates a direction for further research.

My handwriting deteriorates drastically after a few words. It seems as good a way of looking for an abnormal response to exercise as any. A more scientific method would be looking for immune disturbances as people with me indicate immune type problems after exertion in a way that other diseases with post exertional fatigue do not.

 

Isn't that a problem with other illnesses though? For example: someone could be experience MS but without anything showing up on an MRI scan. Likewise someone could have no symptoms but show abnormal signs on scans.

 

The point of tests is not to correlate completely with clinical features - they would be valueless if they did. The point is to tell you something different - something that helps explain, or which gives more objective evidence for future record.

 

that is such a clear statement. Any idea what sort of measurements we might look at being useful?

 

Ha! Apparently not.

I know of an individual who used this as an example when talking to a psychiatrist. She had been taking notes throughout the appointment and showed the notes to the psych to demonstrate what she meant.

The psychiatrist told her that the deterioration in her writing was far more likely to be due to the psychological distress of dealing with the emotions that had been stirred during the appointment.

Whatever test we come up with cannot be open to misinterpretation in this way.

 

I start slurring, swaying and feeling exhausted after talking for over an hour on a 'good day'. Are there tests that measure what is occurring in our brains? It's not the typical PEM I experience from over exerting physically, but it's very debilitating and affects my physical stamina.

 

I think there's a difference between PEM at a level that is triggered by day to day activities and PEM that is triggered by a single or discrete event that might be repeated during the course or a week or month, or not.

In terms of the latter I have at times experienced PEM immediately and at other times have experienced a windows of up to 3 days. I'm thinking of a gentle yoga session (when I was able) for example. A session might only be a couple of poses done at home, not necessarily a class.

In hindsight I am wondering about the 3 day window. I assumed if I didn't experience PEM by day 3 I had gotten away with it but recently it's occurred to me that just because I didn't have obvious signs of PEM within that 3 day window, it doesn't mean something was happening within my body just below the threshold of what I might notice - in the same way your body might be harbouring and mustering resources to tackle a virus asymptomatically for a few days.

The PEM from day to day activities I tend to consider more as a function of my severity level and whether I am in a good phase or bad phase. A lowered PEM threshold possibly.

I'm just trying to get my head around what I think of as PEM vs severity level and how others think of the same thing. It's so easy to assume we are referring to the same things when we aren't. Also what's happening below the water line - if we're not observing symptoms of PEM does that mean we're not in PEM, or is it just below the symptom threshold?

(I think I may have just confused myself here)

 

My PEM always starts within the 12-14 hour window, except for only one time (in 28 years) it started 20 hrs later. I was so happy when I thought I had missed the bullet- but no.

 

I am realising that my fluctuating response to energy using activities is affected by how “poisoned” or otherwise my body is at the time of energy use.

So if I try to ignore really how I’m feeling and simply do something because I can’t resist eg because the sunshine is beautiful in the garden and so I really fancy pottering there for 10 minutes. .(...... I am guessing I am not alone.)
I will immediately feel simply worse and worse.

However if I am feeling OK and my biochemistry feels to be that of a different normal person, then I can potter for 20 - 30 minutes without feeling worse. Then I will pay for that later between 19 to 48 hrs ish. ......depending on how poisoned my body was , which I cannot feel at this level.

In other words even after decades of having this disease, I still am unable to usually feel when my body will react with PEM. Another cause of frustration for me because I usually can’t feel when I have over-done energy usage until it’s too late.

 

Those of us who don't experience too many symptoms have to got by decades of experience, trials and error. In the last 8 years I've decided to reduce my 'energy envelope' just a little more in case I'm overdoing, even without PEM.

 

Not sure about that. But it’s the increase in anaerobic threshold (AT) after exertion that I thought was most significant, when previously it had reduced. I wasn’t very clear though in my original post and didn’t give enough detail. We did the second CPET 18 months after the first one because we suspected she was in remission, as she had the capacity to ‘overdo’ it without exacerbating other symptoms. Also her PEM, being a child when she got ME, always came on much faster, so repeating the test on day 2 was an accurate measure for her.

Test 1 (2018) showed a 42% reduction in AT on day 2.
Test 2 (2019) showed a 58% increase in AT on day 2.

I showed the results to several people whose views on ME I respect, including Dr Paul Worthley and Physios for ME, and all agreed that they showed she could theoretically start to do some gentle exercise/physio and safely increase her functional capacity. In reality, day to day this didn’t work out, as she then had one cold after another over the winter which made us cautious. Ironically we put it off until this Spring to focus on that side of things properly, patience being a virtue with this disease, but the lockdown put paid to that.

Now she’s suspected to have caught Covid as she’s deteriorated since the beginning of May (we were all shielding so not sure how) and not recovering. We don’t know if that has affected her physiological response to exertion yet, so she will re-take the CPET when she’s able to see where it’s left us, and whether exceeding her AT is still safe, or if we’re back at square one where it will have a detrimental effect.

But the reason I raised it is whether this can/should be used as a eligibility criteria for having ME, particularly for DecodeME, and do other people have that depth of measurable knowledge about their condition and capacity (present company excepted, but we’re talking 20,000 participants)? I still don’t really know the answer to that.

We felt that she was in remission and technically was recovering physically from 4 years of ME (where PEM is a mandatory symptom), rather than she still had it. But she registered for DecodeME anyway so they could make that call at the time.

 

I’ve probably addressed this in my follow up post below, but obviously if sometimes her PEM came on up to 3 days later, we wouldn’t think a test 24 hours later would be a reliable measure for her. This is obviously one of the considerations we took into account when determining the validity of the results.

 

@Jonathan Edwards Are you saying that PEM is not what the CPET measures and PEM is something else, or more than, an abnormal physiological response to exertion?

I realise it can give false positives where it doesn’t show a reduction in AT, but where the patient clearly suffers from PEM in some guise. My friend’s 15 yo daughter is a prime example of that. Her AT was slightly higher on day 2, but she has suspected POTS and the paediatric primer states that PEM can also be caused by orthostatic intolerance, as well as exertion intolerance (or something along those lines, it’s a while since I read it). And I‘m also aware that studies haven’t correctly identified all pwme through this method so it’s not foolproof as a diagnostic tool. But could you use it for comparison purposes though, where one test showed deterioration in AT and the next a significant improvement, ie -42% changing to 58%?