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

https://www.tandfonline.com/doi/full/10.1080/21641846.2018.1494530

 

Click here to read the full paper on sci-hub

 

I found this wording questionable: "feeling hot/cold for no reason". I'm sure there is a reason! I get very hot after doing an activity for a while, and suspect that it's due to my delayed adjustment mechanisms. It stops after I've stopped the activity for about 5 minutes.

 

What's the gain of this 6-subclass-category? And I didn't understand the symptom selection criteria for building these classes. Does someone?

 

I haven't read the full paper but do they note duration of illness anywhere?; in my experience you can develop 'new' symptoms and older symptoms can decline in severity as time goes on (possibly due to better management).
So I don't think this approach to sub-sets particularly helpful.

 

https://twitter.com/user/status/1030194799964504064

 

I'm not sure how valuable this study is, like Trish, but now I have read it, I might as well post observations.

 

So people who had the symptom some of the time were included with those who had it none of the time.

 

I don't understand the details but the authors had different options to choose from. The one they chose wasn't the best on all measures.

 

This is the main table. The numbers are the probabilities somebody from a particular class had the symptom (using the 2/2 threshold)

 

I have to wonder with at least some these particular symptoms, how accurately people are reporting them.

People could concentrate on some symptoms more than others.

For example, I remember being more conscious of my heartbeat previously but now I don't pay much attention to it so might say that I don't have an irregular heartbeat, particularly after having normal ECGs.

This could be particularly important if people concentrate on particular types of symptoms.

I avoid standing as much as possible, so don't have as much dizziness as previously.

 

This seems a common enough finding: the more severe an illness people have, the more symptoms they have.

It was interesting previously when Jason did previous studies where people were divided by severity. There was a difference on virtually every symptom. I think in general summing the scores of all the symptoms could be useful to define severity thresholds or even as illness criteria, but Jason seems to avoid wanting to do that.

 

This might put them at odds with supporters of the international consensus criteria, for example.

I think the authors of this study might need to give more specific details to justify this claim e.g. Are these specific symptoms used in a problematic way in other criteria?

 

They do later on go on to say that the classes need to be replicated, so I suppose this is not totally unreasonable. But for the moment, it might be simpler just to treat people by their individual symptoms rather than these speculative classes.

The point with regard to subgrouping research samples may be stronger.

 

It is a little interesting to see the dynamics of applying for disability payments/benefits being discussed in a paper. And though I'm not 100% convinced by all their arguments about prejudice or difficulties, perhaps empirical evidence might show it to be true.

Certainly it seems plausible that somebody with a "relapsing and remitting" illness course might find it more difficult to get disability payments (or alternatively they might be less likely to see the process of applying through, either by not applying at all, or by giving up if they faced difficulties if they then had a good period).

They could have looked at the variable involving a "relapsing and remitting" illness course directly to see if the relationship was stronger or weaker, rather than doing solely relying on the class method.