Search results

Twitter summary: 1) New blog post about the largest 2-day exercise study to date. Big thanks to the authors, Dr. Betsy Keller and colleagues, for uploading the data to http://mapmecfs.org so that others can analyse and explore it. 2) Here are the results for peak oxygen consumption (VO2) which...

"The largest study on repeated cardiopulmonary exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) could not find a strong effect. Declines during the second exercise test are also present in many healthy controls and do not correlate well with functional disability...

Conclusion In conclusion, the largest and highest quality study on 2-day exercise testing did not find strong evidence of impaired recovery in ME/CFS patients. This suggests that the effects are smaller than initially thought and that the procedure has difficulty in accurately differentiating...

Published a blog today, summarizing the data and analyses made here: https://mecfsskeptic.com/the-biggest-2-day-exercise-study/

Conceptually I find it difficult to see why a low value on day1 would make it easier to have a large percentage increase. The way I see it each participant has a hypothetical mean, the average value they would get if they were tested infinite times. There will be some variation around that mean...

Good point, it's probably not a coincidence that the effect is that clear with those 4 outliers removed. For the matched pairs and with those 4 outliers removed I found a Mann-Whitney p of 0.088, which is not significant but it comes close.

Good point but these variations apply to both the ME/CFS group and controls, so unsure how this would cause a (lack of) difference between the two. Regarding the outliers: we used methods such as rank-based tests (Mann-Whitney and Spearman rho) or windsorizing that are not affected by the outlier.

@Snow Leopard You have good grasps on exercise testing methodology and CPET findings, do you have any thoughts on the Keller et al. 2024 data seemingly not showing a significant effect for workload at the ventilatory threshold?

The data in this paper (Davenport et al. 2020) is the same as the data reported by Snell et al.2013. Discriminative validity of metabolic and workload measurements for identifying people with chronic fatigue syndrome - PubMed (nih.gov) This was acknowledges in this 2022 meta-analysis by...

The problem with the Snell et al. 2013 data and it being the same as the Davenport et al. 2020 data was discussed in the review by Franklin. Here's what he wrote: So the research team confirmed that the data was the same but they could not clarify the enormous difference for Workload_AT for...

I doubt it is a solid finding as there has been several studies that could not find a difference with controls. It's mostly this Australian group (and earlier the one by Nancy Klimas in Florida) that has been pushing this narrative. Eaton-Fitch and Marshall-Gradisnik already did a review on...

Unfortunately, I think the data from Van Campen 2021 (both the female and the male study) look suspicious. In the male, study all the ME/CFS patients had increases while all controls with idiopathic fatigue had increases. And this was the case for VO2 and workload at both peak and AT vales...

The data of Lien et al. 2019 on workload at the ventilatory threshold also look weird. How can there be so many datapoints with the exact same value if these represent changes from CPET1 to CPET2. Franklin discarded these in his thesis because Lien et al. could not clarify why the data...

I think that the data in Davenport 2020 and Snell 2013 are the same data. They are from the same research group, both on 51 ME/CFS patients and 10 controls. The data matches almost perfectly except for a major difference for workload at the ventilatory threshold. - Snell 2013 reported a...

Excellent. Agree: their values on each day do not seem very abnormal, not extreme values that suggest a measurement error or something like that.

Had a closer look at this. The problem is that taking the means first and then their percentage change is sometimes different from taking the percentage change per participant first and then taking the mean. This is especially a problem with wkld_AT and time_sec_AT: I thought this was due to...

I used Youden's J statistic the find the optimal threshold, which is just (true positive rate - false positive rate) or written differently sensitivity - (1-specificity). I think visually you can interpret it as the point on the ROC curve that is furthest away from the red dotted diagonal. For...

I think the Nelson 2019 study is interesting. Even though it is quite small, it is one of the few that used an appropriate analysis comparing both the testing difference (CPET2-CPET1) and group difference (MECFS versus HC) at the same time. They also suggest using percentages: They only...

Nice visualization, thanks. One suggestion: it might more intuitive if both graphs have the same scale, so that difference in VO2 and wkld can be compared. Now they look the same size but VO2 has a scale from -20 to 10 and wkld from -50 to 20.

Seems all very speculative (and that is probably an euphemism).