ME/CFS Research Published 6 – 12 February 2024

The weekly research round-up includes all recent publications about ME/CFS and Long Covid, which includes the key terms: Myalgic Encephalomyelitis, Chronic Fatigue Syndrome, ME/CFS, Long Covid and Post Covid syndrome.

The list is inclusive of all research published to keep our community informed, however, this does not necessarily mean we endorse the studies. We briefly highlight and analyse particularly studies which have caught our attention.

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The ME Association maintains a comprehensive index of published research on ME/CFS and Long Covid that is free to use and updated weekly.

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Audio Commentary by Dr Katrina Pears

There have been six new ME/CFS studies and forty-one new Long Covid studies.

We have highlighted one of the ME/CFS studies in more detail below:

Paper four (4) is on assessing post-exertional malaise (PEM) which is a hallmark symptom of ME/CFS. This study aimed at increasing our understanding of PEM and the best way to measure it through semi structured qualitative interviews (QIs) alongside visual analogue scale (VAS) measures after a cardiopulmonary exercise test (CPET).

The Visual Analog Scale (VAS) is frequently used to assess PEM. This scale is designed to rate a person’s intensity to certain sensations and feelings and is typically used as a pain rating scale. More information about this scale can be found here.
Qualitative interviews (QI) can also be used to capture the onset, changes in PEM severity, trajectory and symptoms overtime (including the most bothersome), although data collected through this is hard to quantify. QIs are very useful to compliment the use of VAS and capture information correctly.

Prior to this study, there has been very little validation of the use of VAS and QIs to assess PEM following CPET.

In this study ten ME/CFS participants and nine healthy controls participated in CPET. For each participant, PEM symptom VAS (12 symptoms) and semi structured QIs were administered at six timepoints over 72 hours before and after a single CPET. The data was used to plot the severity of PEM at each time point and identify the self-described most bothersome symptom for participant.

Capturing PEM is known to be difficult, and this study sought to address the problems in measuring PEM. They found that a quantitative–qualitative mixed model approach is needed, as QIs were able to capture changes in PEM severity and symptom over time, even when VAS scales failed to do so. Other findings included:

Each ME/CFS participant had a unique PEM experience, with differences noted in the onset, severity, trajectory over time and most bothersome symptom.
Only one ME/CFS participant returned to their pre-CPET levels within the 72-hour timepoint.
A large variation was seen in the peak timing of PEM, with several of the participants reporting more than one peak in PEM (which was unable to be captured using VAS alone).
Most bothersome symptoms were captured through QIs- physical fatigue (40%), mental fatigue (20%), headache (30%) and muscle ache (10%).
No healthy volunteers experienced PEM.
QI and VAS captured information differently about the course of PEM, with QIs having a more measurement of granularity and face validity.
QI and VAS fatigue data corresponded well an hour prior to exercise but poorly at peak PEM and with the change from pre-CPET to peak.
When the most bothersome symptom identified from QIs was used, these correlations improved and reduced the observed VAS scale ceiling effects.

A few things to note about this study:

This research is part of a larger NIH study looking into phenotyping of ME/CFS and healthy controls through a CPET intervention designed to induce PEM with serial follow- up performed over 72 hours.
All ME/CFS participants met the IOM 2015 ME/CFS diagnosis criteria.
Where possible healthy controls meant the same demographic characteristics of the ME/CFS participants (age, sex etc). Although there is not information of whether the controls were sedentary.
QIs were conducted before VAS, so its not know how this would have affected the results if done in the reverse.
It would also have been useful in this study to combine the DePaul Post-Exertional Malaise Questionnaire (DSQ) which is another common tool to assess PEM.
It is a shame no biomedical samples were taken to further support the results, for example measuring lactate levels, with more elevated levels been previously found in more severe PEM.

This was a very small exploratory study showing that QIs are more sensitive to PEM than VAS, although it questions how feasible this would be to conduct on a larger scale (interviews are time heavy for both researchers and participants). Furthermore, I do not feel this study tells us anything new about the PEM experience of people with ME/CFS.

You may also be interested in reading our previous review on the evidence for post-exertional malaise (PEM) in ME/CFS and Long Covid, which can be found here.

ME/CFS Research References

Long-COVID Research References

Dr Katrina Pears,
Research Correspondent.
The ME Association.

RESEARCH INDEX

Audio Commentary by Dr Katrina Pears

ME/CFS Research References

Long-COVID Research References

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