We need a diagnostic test for fatigue induced by sustained activity

Cardiopulmonary exercise testing tests the capacity to do high-intensity activity for about 10 minutes.

A neurological examination tests whether the muscles and nervous system permit normal movement for a few moments.

These tests are useless when the problem is the inability to sustain exertion over the course of the day. If exertion cannot be sustained, then the person won't be able to work or study or even take care of themselves at home. The patients so affected learn to manage the problem by staying within their sustainable limits, but this is easily confused with laziness.

The inability to sustain exertion is highly underestimated and I think this is because there are no practical tests.

What kind of tests have the potential to measure the impact of sustained exertion?

 

It really depends in what the impact is, both on a molecular basis and on a functional capacity basis.

FUNCAP is the best option with regards to the limitations people with PEM face.

 

Do we need a test, though? If there were one, would it tell us anything we don't know?

We do need an explanation, but I'm less sure about a test. Maybe it partly depends on who the test is for.

There aren't tests for chronic pain, for instance, and those complaining of it are often doubted. But would it solve the problem if it could be measured or shown on a scan? People who're inclined to doubt would still be inclined to doubt, and would probably look for another justification. Being shown evidence rarely changes attitudes.


[Edited slightly, because it read as if it were a strong challenge to the OP. It was only meant to be me musing aloud!]

 

The physiosforme pilot where they measured people in their home was an important step here I think

because of the cumulative and all the little differences that can turn one activity from one energy bracket to another - eg standing up, noise or divided attention, hot day, just having to also listen out for an alarm whilst stirring a pot.

So the idea setting arbitrary schedules of tasks when people have different heights, types of disabilities and comorbidities and living conditions (including home layouts, better beds for rest or a recliner nearby etc) doesn’t involve like with like.

but if they can start from when someone wakes (naturally), make sure they haven’t exerted before at different levels (probably means it is in bed) and find something they can somewhat make consistent (might involve noise cancelling headphones etc) they can at least have a measure of how that ‘somewhat sane thing’ affects different people. But also then how it varies across different days (based on what else they have done in days leading up) so we can see what ‘can’t looks like’?

but of course even that becomes tricky because in pem just the when you (can) wake up gets changed. And those who get that have historically ended up as drop outs rather than this part of the data counted.

it’s conceivable that at least we might find measures that can show if/where an activity can be high exertion on a bad day vs lower on a good.

oh I’m not there yet!

 

More importantly: would it be considered valid and used correctly? I doubt there is such a test. Medicine does not have the tools for this, even less the motivation or interest. They don't have the cognitive tools for it, the mental flexibility.

When we compare with brain fog, we're dealing with a huge number of people who lose most cognitive function, can't do basic math, can barely read, have no executive function anymore, and not a single test has so far conclusively shown anything. People who can't do the easy parts of their job anymore, and there isn't a single test that has captured this in a useful way. Because they don't know how to test what they don't understand. And they don't understand what they can't test for. Which is super great! I love this damn permanent Catch-22 so much!

Frankly, I don't think such functional tests are relevant, they can always be argued and dismissed on whims. The only tests that matter to physicians involve biology. That's not entirely true in all things, but for health problems they don't believe in, it's an absolute truth. As time passes they just keep raising the bar to accept it, and the bar has been set to only accept a fully reliable biomarker, at a minimum. They'd probably want effective treatments as well, which is the bar that peptic ulcers had to pass.

We need such a test, but more than that we need medicine to know what the test means. And they need to come up with it. And accept it. And validate it. And make it available and used. I don't think they can do that, and even in the very best case, it would take a minimum of two decades. Researchers new to this type of problem are still clowning around with the CFQ. They can literally waste decades on useless questionnaires of zero value, because they don't even understand what the problem is.

We need a reformed medical profession more than we need that test, because without massive reforms, no such test can be developed. It would be like expecting an old aristocracy to come up, all on their own and voluntarily, with a fair democratic system. There are tall orders, and then there's this, in which all the tall orders stand in its shadow.

 

I love this idea. I think it’s workable. You could find people with similar levels of ME, similar home circumstances, age sex etc so that the group are homogeneous . It’s at home so big tick there. And deteriorating to the point of having to drop out tells us something, too, if you actually can’t continue being monitored in your own home!

 

I'm sorry to disagree, I think FUNCAP is inadequate. While it does acknowledge the possibility that one type of activity can lead to a reduction of activities on the same day, it is still centered on the view that it is the type of activity that is problematic, and not the cumulative dose of activity.

FUNCAP treats the activities as if they're indipendent of each other, while a normal day contains a lot of different activities, that if considered in isolation, may not be sufficient to cause significant fatigue and/or PEM, but that when combined, are impossible to sustain.

All activities are problematic with sufficient dose or if the cumulative dose exceeds tolerance limits. At the same time, few or none of them are problematic if the cumulative activity dose for that day is low enough.

We need to measure the cumulative activity dose that can be sustained and compare it to that of healthy people. This will be much more accurate.

 

When I saw the title, I assumed a biological diagnostic test, meaning biomarker. That would be useful. Imagine if they tested the "chronic fatigue" symptom in PWME and found that they didn't show the marker for normal fatigue. Downside is that the BPS crowd would claim that as proof of their nonsense. Upside is that someone would research what causes fatigue-like symptoms.

 

However, the type of activity still matters, since the response to dosage varies with the activity. For me, less than a minute of window washing or ladder climbing was more likely to trigger PEM than hours of bike riding. The determining factor seemed to be how accustomed my body was at doing an activity. I suppose that if I'd washed windows many hours a week and didn't ride, then the unaccustomed stationary bicycle test would have triggered PEM.

 

Does it though? It asks you about the believed consequence of doing activity X during an average day the last month.

Is that activity in itself enough to influence how much you can do the rest of the period?

Finding your threshold serves as a proxy for how much you could do that month, all things considered.

This would be better, but not exhaustive because I’m not convinced that PEM is exclusively accumulated. I’m pretty sure I’ve had very activity specific PEM, although it’s impossible to confirm.

 

FUNCAP isn't useless, it's just inadequate.

A person is disabled if they can't perform a normal amount of ordinary activities of daily life for several days every week.

In my experience this happens at a much lower severity level than the one where PEM begins being triggered by relatively short exposures to specific kinds of activities.

That shows FUNCAP is not good at capturing the problem.

In my mental model of the problem, what matters is the total amount of exertion on each day (which varies by activity, but in the end they all contribute to PEM and fatigue) and whether the body can recover from it.

The PEM that is activity specific may be specific mainly because that activity necessarily involves a large enough dose of exertion and PEM-inducing stress. So asking about PEM being triggered by specific activities may be just an indirect way of asking about dose of exertion.

 

I don’t think anyone has argued that it is perfect. I believe I said it was the best, as in the best we’ve currently got.

FUNCAP doesn’t ask about if you got PEM. I’m not sure I follow your argument, but that might very well be a me problem!

 

I never noticed PEM from accumulated exertion. I always considered it to be triggered by specific actions (unaccustomed strain on muscles).

 

Yes, of course we need a test to prove ME is real. We need to be treated with consideration in order to minimise deterioration of our condition. There are people struggling to get benefits, accommodations at work, appropriate housing, etc.

Evidence does change minds, look at this comment:

 

IMO, we don’t need a test to prove that ME/CFS is real.

But it would be very helpful to have one for a lot of reasons. So we definitely should work on inventing one.

 

What do we mean by ME/CFS being real?
A clinical category?
A biological difference?

How would ME/CFS being real fit into the possibility of there being multiple illnesses (and maybe other things) that compromise the clinical construct of ME/CFS.

Was “dropsy” real? (broadly a term used to describe a clinical construct that was comprised of illnesses we now know as kidney disease, congestive heart failure, and a lot more.)

If I understand this conversation, maybe ME/CFS being real would mean that having ME/CFS would be seen as a valid experience. In that case, we shouldn’t need a test to show that.

 

That the symptoms and disability we experience are real. The cause or causes do not matter for the ‘realness’ of that.

 

But people have not denied that symptoms and the disability experienced aren't "real" in the sense of them existing. Garner et al don't argue that what people experience doesn't exist, they argue that it's a concoction of mind-body interactions that can be healed with CBT/GET.

 

A test will not change that because they believe that the mind body interaction can cause anything to happen. So the mind body interaction caused whatever change a test measures, according to them.

 

Yup, there are conditions that do have tests (or pathology that shows up on scans), but people's testimony about their disabling effects is still doubted or denied as soon as money is involved.

Unless it's a devastating fatal condition, a test seems unlikely to make much difference in the context of social or employment support. The starting assumption will always be the same: you're lying or exaggerating.

It would help with diagnosis, but even that can be a lot less straightforward than it looks.