Latent class analysis of a heterogeneous international sample of patients with myalgic encephalomyelitis/chronic fatigue syndrome (Leonard Jason team)

Frank Twisk replied:

Extract:

I remain to be convinced that cognitive symptoms should not be a requirement. It seems to weak to base this on one study. It would be interesting to see the particular wording. The studies I recall in recent years had a much higher rate of cognitive symptoms.

 

@Dolphin, thanks for wading through this.

A few thoughts:

Jason is resisting the notion that counting the number of symptoms can be used as an indicator of severity. You wondered why this might be. I'm wondering whether it's that old psychiatric belief that 'more symptoms = more likely to be psychosomatic' getting in the way.

Maybe he feels counting symptoms will include too many of these 'psychosomatic' patients? My feeling is that this is a nonsense concept, given weight because people with more complex symptoms will also have more complex illnesses, which cursory investigations may not capture. (I.e., I don't really believe there's much evidence for purely psychogenic somatic illnesses.)

You mention the Twisk comment. I'm with you that one study (which still shows that 77% of patients do have brainfog) doesn't mean brainfog isn't a core symptom.

However, perhaps more importantly, we don't know what the basis for this four 'core' symptom criteria are. It's unlikely to be the SEID definition (which Jason doesn't seem to like, considering his papers on subject), but in that definition, it's a choice of OI or cognitive problems, not necessarily both. Is that the case here? Do we know whether the paper requires all four 'core' symptoms to be present in everyone or does it require, for example, three out of four?

Lastly, is there a quick and concise summary of each subgroup?

Edited: second use of 'symptoms' should have been 'illnesses'. Now corrected.

 

Yes, he has expressed that concern before.

 

I suffer from cognitive problems both in PEM and out. What I’ve noticed though is that the severity increases with PEM this manifests as:
Confusion (I.e. can’t think straight)
Poor concentration
Poor hand to eye coordination
Blurred vision
Sensitivity to light
Sensitivity to sound
Poor memory

I track these separately. What I’ve noticed is that all of these coincide and are heightened with PEM but only some are present all the time as a continual base symptom that fluctuates from day to day (confusion, poor concentration and memory loss)

I think you could iron out questionnaire error by making the subjects carry out a tracker symptom diary. I’m surprised that any author would publish without sense checking responses in some way? This is particularly odd since the symptoms wax and wane over time?

Personally I think cognitive dysfunction is/are one of my most restrictive symptom/s so excluding it seems a little weird particularly as it’s so common?

 

It is unclear to me whether there were any requirements for specific symptoms:

 

But there is no test for any of it? You can’t test PEM for example even though it’s diagnostic based on patient accounts. So why not cognitive problems alongside muscle fatiguability and PEM?

77% seems quite high to me ?

I don’t suppose it matters because it’s not up to me either

 

I think the best criteria may be by obtained by summing scores of symptoms, including severity and frequency.

But if one wants required symptoms, after postexertional malaise, cognitive symptoms and unrefreshing sleep show up in the highest percentage of patients from what I have seen, usually in the 90s%.

 

I used to think recovery of muscle strength might be useful as a required symptom.

But studies like this make be question that. Even the results of the repeat exercise tests are not that clear-cut in many ways.

http://www.meresearch.org.uk/our-research/completed-studies/upper-limb-muscle-function/

 

Thanks. So the subgroups are entirely defined by 'secondary' symptoms and seem to divide as follows:

Class 1 - All or most secondary symptoms
Class 2 - GI
Class 3 - GI and circulatory problems
Class 4 - Circulatory problems
Class 5 - Circulatory problems and OI
Class 6 - no secondary symptoms

CCC and ICC seem to select for Class 1, but less well for other classes (which comprise ~60%).

It seems that, if Jason is right, a modified four-symptom criteria could be developed with optional secondary criteria to define subgroup.

 

Note that there were lots of other symptoms that were more common than the symptoms looked at but not as common as the “core” symptoms that were not included in the analysis. They might work better to form subgroups.

 

The CDC empiric criteria (Reeves et al, 2005), an operationalisation of the Fukuda criteria, used this method.

https://bmcmedicine.biomedcentral.com/articles/10.1186/1741-7015-3-19

So you had to have at least four out of the eight Fukuda criteria symptoms. Each symptom scored 0-16 based on how frequently people had it, and the severity of it.

The total required to be diagnosed was 25.
As I recall, they picked this number out of the air.

I think it would be interesting if other thresholds were looked at using a bigger set of symptoms. I find it disappointing that Leonard Jason and his team haven't done that.

 

My thought is that trying to define subgroups in the abstract is never a very useful exercise. Subgrouping can be very useful but on the whole each scientific or clinical issue you want to tackle is likely to benefit from a different way of subgrouping. For instance it can be useful to divide diabetes into non-obese and obese, or into insulin resistant and non-insulin resistant. The divisions may work out mostly the same but for different questions either one or other way is the better way to subdivide.

I have not read this paper but I do not get the impression that the subdivision is tailored to any very specific question.

 

I think I remember some of our members here saying that they have the physical symptoms but not the cognitive ones, which surprised me, but I also found very interesting. One thought is that something like cancer, though at the top level can be thought of as the same disease, affects sufferers very differently in some ways according to which part(s) of the body it attacks. Could ME be something which although essentially the same disease mechanism, affects people differently according to which parts of the body it affects?

 

I think brain fog is possibly apt for some members because their cognitive symptoms are not as severe as others.
@Trish Thank goodness we have some MEs like you who don't get the brain symptoms as bad as other MEs. You write so well and we need good speakers and writers like you.

I find the term brain fog an understatement of what I have experienced. I've never liked describing my brain symptoms as brain fog. What happened to me at my mild ME onset was shocking. I had a major change in brain function. So severe that I could no longer study. I had to drop out. It's been constant without change these last 20 years. Something significant happened. Brain fog is far too trivial a way of describing this change for me.

Some of us get hit harder in some areas more than others. After reading about other MEs gut problems in ME I feel I got away much more lightly in this area even though my gut was bad in the severe years, still not as bad as others.