S4ME: Submission to the public review on common data elements for ME/CFS: Problems with the Chalder Fatigue Questionnaire

Could the mental fatigue and physical fatigue be "measured" using separate questionnaires? Or does that make things over-complicated? The Chalder thing is a load of carp anyway, so why not make something better for both fatigue components. Oh, and when it comes to having problems with starting things, I have no problems with that. Now finishing them is a different matter of course!

 

Yes I was thinking more about the scores we use in food rating. There are a number of different ones depending upon what you plan to measure (discrimination tests would be used to measure difference, acceptance tests for approval rating and just right for determining if things are too little or too much). For most of these the test methodology originated out of NASA or the USA army and were tested ad infinitum in the 50's and 60's. Most marketing survey companies adopt some of these principles although I've seen quite a few howlers though that did need to feel the point of my pencil.

It does seem difficult to fathom what TC had in mind when she designed this, but I seem to recall people have used it as a screening tool subsequently (that might be brain fog of course). Either way its not very good for either job (I'm being polite and nearly used one of @Woolie descriptive pictures but refrained)

 

Many thanks for that Adrian, very helpful once I got my head round it.

This part of your post was what I mainly had in mind:

The problem reminds me of an engineering example, where high temperatures are typically measured using thermocouples; temperature changes result in small voltage changes, but the transfer characteristic is often very non-linear, the voltage change varying considerably for a given temperature change, depending what the temperature actually is. The big advantage in this case is that the characteristic is very well known, and so the appropriate compensation can be applied, so what you end up with is a linear relationship between volts (mV actually) and calculated temperature, via the characterisation step.

I would think it very unlikely there is going to be a neat linear relationship between actual fatigue (as you say, whatever that is), and people's rendering of it onto something like the CFQ. But unlike my thermocouple example, the characteristic is far from well known I image, or even well recognised. Yet without understanding that relationship, it could be that someone being interpreted as twice as fatigued as someone else, might for example actually be four times more fatigued, or whatever. Presuming a neat cosy relationship would be a bad idea, unless already proven to be neat and cosy, which I very much doubt.

Have any studies ever been done I wonder to try and better understand the characteristic that relates a person's actual "fatigueness", with their reporting of it into something like the CFQ? Very tricky I imagine, even if the will is there.

 

There is a closer analogy when considering the decibel scale, and noise perceptions. This link ...

http://www.noisehelp.com/decibel-scale.html

... sums it up nicely with:

Somewhere in the past someone must have done some experiments to identify this relationship. Interesting that they will have been using an objectively measurable value (acoustic power) to then assess people's percepetions of loudness. In fairness, I imagine the physical characteristics of the ear play a significant part in things.

 

I'm just going to throw my twitterings into the ring... https://twitter.com/user/status/847828312730853377


Good critique by Carolyn and Graham. There are so many problems with CFQ that it's difficult to know where to start!

The key one for me was the use of different time periods in the instructions. "In the last month" is underlined on the scale commonly used. And although the instructions tell you to compare yourself with "when you last felt well", this then poses a conflict if you repeat the questionnaire several months later, particularly if the intervention has fiddled about with your definition of what is "usual" (particularly as the first few weeks of the intervention will be about establishing new baselines).

It also strikes me that it is terrible choice of instrument if you want to capture "improvement", because it is so heavily weighted towards getting "worse".

Hence my summary:

CFQ should only ever be used as a diagnostic tool (and probably only to diagnose Chalder Fatigue Syndrome). It is NOT a repeated measures instrument. It does NOT measure absolute fatigue. It is NOT suitable for use as a trial outcome measure.

My bloggings are here (in case anyone is interested):
https://lucibee.wordpress.com/2016/04/02/fatigued-by-scales-as-outcome-measures/
https://lucibee.wordpress.com/2017/03/30/more-on-fatigue/
https://lucibee.wordpress.com/2017/03/31/even-more-on-fatigue-getting-really-tired-now/

 

I can't imagine enjoying the luxury Wooly suggests -- of basing my movements on some intellectual prediction of how they will make me feel the next day. I simply find myself unable to move further. Nor do I feel "fatigue." I feel that I have no further capacity. My body fails or my brain fails or both. "Exhaustion" would be a more accurate word than "fatigue." With "fatigue" one feels poorly but can carry on. With ME one finds oneself -- often many times in a day, or continuously -- simply unable to carry on. The essence of "PEM" in ME is the inability to move, the inability to recover and the inability to resume in respect of normal human activities.

 

Since I spend about 80% of my time bedbound (physically, I'm on the more severe end of the spectrum), I feel a little offended at the idea that there's anything "luxurious" about my situation. But I'm figuring you didn't mean it that way, @deboruth.

What you say does point to the idea that different people might have different illness mechanisms.

So here's my thought. There's a group of us where the primary problem is to do with inflammation. This inflammation is stimulated by exertion. When stimulated we feel awfully sick, flu-like, with lots of burning and aching and headaches. These effects are often delayed (for example, they may peak the day after the exertion). So our main goal is to keep these symptoms to a minimum - hence, avoidance of PEM. I'm almost certainly in this group.

Then there's another group where the problem is primarily to do with energy production. People in this group talk in terms of a battery - once the energy's used up, that's it. @deboruth, your description suggests you might be in this group.

I do occasionally get what you describe as collapse if I push too hard, but its more like burning, screaming pain than a feeling that I've run out of energy. More often though, I push through with no immediate symptoms, not till the next day. But then the price may be severe malasie, burning, headaches, so bad I might not be able to move my head for days. Its all very episodic so its easy to send yourself to bed for a fortnight, then feel a little better one day, do a few small things and then start the cycle all over again.

 

I suspect it has been "validated by opinion".

 

I suspect that we are here getting to the nub of a part of the problem. There is a variety of types of fatigue expressed in different ways, over different time scales. Some people may suffer two or more types of "fatigue", all of which may be different to what others suffer.

If people, who shall be nameless, had been doing there jobs, this might have been noticed by them. But we learned from "Reviewer 2" of the attention to detail displayed in the collection of histories.

 

I suspect there may be a strong commonality in underlying problem, and the difference may be more to do with manifestation.

I would be very surprised if significantly restricted energy availability isn't core to what all PwME experience. But it may be that for one group, their normal safety mechanism of fatigue kicks in to warn them their energy supply is dropping through the floor, and they need to back off; albeit for PwME it typically kicks in much too late (probably because their energy availability drops off so rapidly, maybe after a time delay), hence the need for pacing. My wife would be in this category. But by the sound of it there is perhaps another group where maybe the normal fatigue safety mechanism just doesn't kick in at all, and the first the person knows about it is when their energy availability drops though the floor.

 

Yes, I wondered that too, @Barry, since inflammation seems to interfere with cellular energy production.

Yes, I think that's the whole reason people are encouraged to learn how to pace. For most of us, our bodies don't always tell us to stop early enough. If it did, then we wouldn't need to learn to pace.

 

My brain is mush so i wont comment on the details of whats being said here but will say that i've agreed with all the comments so far. The CFQ is a joke. It's a pity its consequences are far from funny.

Well done everyone for all your comments & submission, much appreciated

 

Yep. Sound level is logarithmic scale. Noise and distance. Db levels are adjusted ( weighted) for human hearing range too

 

I don't think distance has anything to do with it directly. You could sit someone in front a speaker at some distance and leave them there, and have some form of acoustic power meter at the same position. Then you set the acoustic power at say 1W, and the person has some sense of its loudness. Then wind the amplifier up until the acoustic power meter shows 10W, but the person will perceive the loudness to have only increased by a factor of 2, not 10. At 100W (ear drums permitting) the person will sense the loudness to be 4 times what it was at 1W.

But coming back on track a bit, the relationship between objectively measured sound power, versus subjectively measure loudness, is a very well understood relationship that fits a nice neat mathematical transfer function. For fatigue perception versus "real fatigue", no such neat relationship is known, nor is it even acknowledged as needing to be understood. It's just a case of "Trust me ... I'm a psychiatrist".

 

Shame the objective/ subjective wasn' t researched as well as in acoustics.

Thought i was going a bit mad, as i was taught the relationship between sound ( amplitude) and distance. There is a relationship ( phew! Brain still there at times- i did acoustics a long time ago)
Sound power is independent of distance- sound pressure is a distance dependent effect. Db relationship to sound pressure ( amplitude), and intensity ( energy) - for these there is a drop of around 6dB for every doubling of distance. Just in case a pub quiz question comes up ....

 

Yes I think that must also be right. Inverse square law presumably, similar to light intensity.

 

I'm less worried about whether the underlying relationship between ratings and fatigue is linear or logarithmic or whatever. I just want there to be a relationship.

We can worry about scale when we've got that first part right.