Comparing Idiopathic Chronic Fatigue and ME/CFS: Response to 2-day CPET, two papers males & females, 2021, Van Campen & Visser

The suggestion of doing a CPET every day for a fortnight:

If you have someone who loses apparent fitness on the second CPET, ie they haven't recovered from the first CPET and may trigger PEM if they then don't rest for several days to return to their day1 level, why would you suggest doing repeated CPET's over further consecutive days? That would surely be unethical, as, like GET has done for many patients, it would be risking permanent worsening.

 

I would do it, because if there is a constant decline during that period, it says a lot about how GET is damaging. And I don't want my son and all the other young people now and to come to have to live in a world where the BPS view about ME/CFS has credence.

...Well, maybe I'd do a week. And you could stop if people became ill. I felt fine on the second CPET, but my performance dropped by 20%.

 

I don't think we can know that from the information in the papers. They say the CPETS were done to assess exercise intolerance. It seems unlikely that the male study did not have a single person diagnosed with ME/CFS who did not show a drop in performance. That's a pretty impressive diagnosis rate if the CPET had no influence at all on the diagnosis. You might be right, I just think we can't know.

 

Fair enough, it certainly wouldn't be for everybody. But people are still talking about GET trials, and trials of CBT to convince people they need to increase their activity levels - and ethics boards are approving them. People are putting their health at risk every day already.

If you got a handful of people and had them do multiple CPETS, and documented the impact day by day, I think you'd have something very compelling that might cut through all the BPS nonsense and change the situation for people with ME/CFS. I doubt any researcher would be interested of course.

 

It's not about being a diagnostic marker - it's to demonstrate that there is a real consequence from exercise, that it can make people very sick. And exercise every day has a cumulative effect. Still, many people do not believe that. If there are CPETs, there is data to accompany what people are saying about how they feel.

 

Yes, but look at the change in Vo2 at the ventilatory threshold in both males and females:

Male

Female


The split looks suspiciously too perfect for the paired CPET to not be playing some part in the diagnosis decision. I mean, assuming the diagnosis was made before the CPET, what if an ICF diagnosed person did the paired CPET and had a significant drop in performance on the second CPET? Wouldn't the clinician be likely to look hard at the diagnosis, and change it to ME/CFS?

And if someone was definitively diagnosed with ICF, why would they then do the paired CPET for insurance purposes? Surely they would only do that if there was some chance that the diagnosis would be changed?

The difficulty is in knowing whether the authors consistently used an initial diagnosis, or the most recent one, or a mix of both. I don't think they tell us in the papers. I hope I'm wrong and the diagnoses used come from the first diagnosis the patient is given, prior to doing a paired CPET. But the data is from clinical notes - it's almost certainly not as clean as data from a specific trial would be, and therefore less credible, even if the clinicians said now that a pre-CPET diagnosis was used in every case.

Also, if insurance is a big reason for doing the test, the patients have a big incentive to show the performance drop. I haven't read the paper for information on the effort made. But @Snow Leopard has already mentioned it, and I'm sure can tell us more.

 

Sure, I'm just not sure what RERs were reported in the studies- I haven't looked. @Snow Leopard mentioned about effort perhaps being less than full based on heart rates.

Edit - the RERs look fine >=1.1 in both males and females, ME/CFS and ICF.

 

For the female study, there were 24 people diagnosed with ME/CFS and classed as severe who somehow managed to do two CPETs, appropriately spaced. They were left out of the analysis due to them not being appropriately matched with the ICF, which is fair enough.

Van Campen did a study comparing severe patients with mild and moderate ones, discussed here:
Two-Day CPET in Females with a Severe Grade of ME/CFS: Comparison with Patients with Mild and Moderate Disease. van Campen et al. 2020

 

On that thread, @wdb mentions a study that had people with ME/CFS and controls do paired CPETS (Lien et al, 2019)
Abnormal blood lactate accumulation during repeated exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome
The chart below is comparable to the ones from the Van Campen and Visser study in terms of what is being measured. But look at the spread of change in Peak VO2 in the ME/CFS and controls. And then look at the charts my post #34 above, the green sides. The Van Campen and Visser ones have the two cohorts well separated; in the Lien one, even the controls are mostly decreasing from CPET 1 to CPET 2, and the spread of values is quite different, even though the units are the same.



That Lien paper is discussed on S4ME.
Snow Leopard suggests that the problems with the Vo2peak result is that patients have not been exercising to their true peakVo2 across all the studies.

When I did a paired CPET, I did not feel as though I had got near my limit when I was stopped, but my RER was 1.1.

But, if it's a matter of not exercising to the true VO2max, it makes things pretty complicated, with the controls in that study also doing worse on the second CPET.

Perhaps we have to look only at Ventilatory Threshold data - as that isn't confounded by peak effort issues.