Peak Oxygen Uptake in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: A Meta-Analysis. Franklin et al., 2018.

Peak Oxygen Uptake in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: A Meta-Analysis.
Franklin JD, Atkinson G, Atkinson JM, Batterham AM.
Int J Sports Med. 2018 Dec 17. doi: 10.1055/a-0802-9175. [Epub ahead of print]

Abstract:

"To evaluate the magnitude of the difference in VO2peak between patients with Chronic Fatigue Syndrome/ Myalgic Encephalomyelitis (CFS/ME) and apparently healthy controls, 7 databases (Cochrane, PubMed, PsycINFO, Web of Knowledge, Embase, Scopus, Medline) were searched for articles published up to March 2018.

Search terms included "chronic fatigue syndrom*"AND ("peak" OR "maxim*" OR "max") AND ("oxygen uptake" OR "oxygen consumption" OR "VO2peak" or "VO2max". Eligibility criteria were adults>18 y with clinically diagnosed CFS/ME, with VO2peak measured in a maximal test and compared against an apparently healthy control group. The methodological quality of included studies was assessed using a modified Systematic Appraisal of Quality for Observational Research critical appraisal framework.

A random effects meta-analysis was conducted on 32 cross-sectional studies (effects). Pooled mean VO2peak was 5.2 (95% CI: 3.8-6.6) ml.kg-1min-1 lower in CFS/ME patients vs. healthy controls. Between-study variability (Tau) was 3.4 (1.5-4.5) ml.kg-1min-1 indicating substantial heterogeneity. The 95% prediction interval was -1.9 to 12.2 ml.kg-1min-1.

The probability that the effect in a future study would be>the minimum clinically important difference of 1.1 ml.kg-1min-1 (in favour of controls) was 0.88 - likely to be clinically relevant. Synthesis of the available evidence indicates that CFS/ME patients have a substantially reduced VO2peak compared to controls."
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I think this is interesting. There was allready a review on exercise tesing in ME/CFS by Nijs but this one pooled the VO2peak data.

They found data in 32 studies (quite a lot) but they included studies that used the oxford criteria. Perhaps someone should write a letter, pointing out that the NIH and AHRQ said these criteria can be misleading/harmful and ask how the figures turn out if such studies are excluded (I suspect the Oxford studies report less differences in VO2peak but not exactly sure).

They've found a clinically significant difference: the pooled mean VO2peak was 5.2 ml.kg− 1.min− 1 lower in CFS/ME patients than in healthy controls, but there was a lot of between-study variability and half of the studies used no criteria to assess if maximum effort had been achieved.

 

The Oxford criteria probably select a significantly less ill population. Excluding Oxford criteria studies from the analysis would therefore probably result in more marked differences between controls and patients.

A closer look at the differences between Oxford criteria and non-Oxford criteria studies might reveal other interesting differences.

 

I'm confused: if Oxford patients are less ill wouldn't that result in less instead of more differences between patients and controls? [EDIT: sorry I misread: Oxford studies would probably show less differences so excluding them might indeed result in a larger mean difference]

Just thought this study might be an ideal opportunity to point out that we no longer accept Oxford criteria- studies as relevant to ME/CFS. It think this concerns only a few of their 32 studies so results will probably only change a little bit.

 

I think I managed to confuse myself too, and have edited my post.

There is a tricky problem in that excluding Oxford would (in my opinion) quite predictably give a stronger illness signal, but it's unclear whether that is due to selecting a more ill population or because Oxford criteria are too unspecific (many think they are too unspecific).

 

Shouldn't this be included in any new Cochrane review on exercise and ME/CFS?

 

I know of another meta-analysis that suggests the opposite - studies do not consistently show VO2peak on the first/only CPET. The reason for inconsistent results is that patients in some studies aren't actually exercising to their true VO2Max due to lack of consistent motivation between studies.

There are several unpublished 2 day CPET studies which conclude this (no difference in VO2peak).

 

Interesting, do you have a link or reference?

 

The meta analysis I'm talking about was at a presentation and I'm expecting/hoping it to be published soon.

 

That’s annoying, as the repeat day cpets are where the impairment becomes really obvious

Do you have another link? This one is coming up with an error (local host can’t be reached)