Trial Report Mixed methods system for the assessment of post-exertional malaise in myalgic encephalomyelitis/CFS: an exploratory study, 2024, Stussman

Free fulltext:
https://neurologyopen.bmj.com/content/6/1/e000529

Mixed methods system for the assessment of post-exertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: an exploratory study

1. Barbara Stussman1,
2. Brice Calco1,
3. Gina Norato1,
4. Angelique Gavin1,
5. Snigdha Chigurupati2,
6. Avindra Nath1 and
7. Brian Walitt1

1. Correspondence to Ms Barbara Stussman; stussmanbj@mail.nih.gov

Abstract

Background

A central feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is post-exertional malaise (PEM), which is an acute worsening of symptoms after a physical, emotional and/or mental exertion. Dynamic measures of PEM have historically included scaled questionnaires, which have not been validated in ME/CFS. To enhance our understanding of PEM and how best to measure it, we conducted semistructured qualitative interviews (QIs) at the same intervals as visual analogue scale (VAS) measures after a cardiopulmonary exercise test (CPET).

Methods

Ten ME/CFS and nine healthy volunteers participated in a CPET. For each volunteer, PEM symptom VAS (12 symptoms) and semistructured QIs were administered at six timepoints over 72 hours before and after a single CPET. QI data were used to plot the severity of PEM at each time point and identify the self-described most bothersome symptom for each ME/CFS volunteer. Performance of QI and VAS data was compared with each other using Spearman correlations.

Results

Each ME/CFS volunteer had a unique PEM experience, with differences noted in the onset, severity, trajectory over time and most bothersome symptom. No healthy volunteers experienced PEM. QI and VAS fatigue data corresponded well an hour prior to exercise (pre-CPET, r=0.7) but poorly at peak PEM (r=0.28) and with the change from pre-CPET to peak (r=0.20). When the most bothersome symptom identified from QIs was used, these correlations improved (r=0.0.77, 0.42. and 0.54, respectively) and reduced the observed VAS scale ceiling effects.

Conclusion

In this exploratory study, QIs were able to capture changes in PEM severity and symptom quality over time, even when VAS scales failed to do so. Measurement of PEM can be improved by using a quantitative–qualitative mixed model approach.

-------------

WHAT IS ALREADY KNOWN ON THIS TOPIC

• Cardiopulmonary exercise testing (CPET) is an important tool for evaluating post-exertional malaise (PEM), a central feature of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Assessment of PEM following CPET lacks a validated quantification tool.

WHAT THIS STUDY ADDS

• This mixed-methods study used qualitative interviews (QIs) and visual analogue scales (VAS) to assess PEM following CPET. QIs capture the multidimensional experience of PEM, and its change over time, more effectively than VAS. Singling out the most bothersome symptom improved the VAS assessment of PEM.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE, OR POLICY

• This study provides insights into potential methods that can optimise the subjective assessments of PEM.

 

Barbara Stussman of NINDS had previously published an underwhelming Focus group-type study of PEM, though maybe this one - which seems more useful - is part of the same study.

 

I don't see the "quantitative" portion of this study, unless they are calling QI quantitative. That would be oxymoronic if they did.

 

The results from the visual analogue scale (VAS) = quantitative data?

 

Only skimmed part of the paper -- how they measured PEM. Thought there are a couple of points worthwhile to discuss:

"All interviews were conducted bedside in the volunteer’s hospital room with one study team member observing, except for the 4-hour post-CPET interview, which was conducted via telephone due to the volunteer undergoing respiratory exchange measurements in a metabolic chamber."

"Each interview lasted 30–45 min and was recorded and transcribed. By performing an assessment before undergoing CPET, we established each volunteer’s pre-CPET level. We sought to fully understand symptoms following CPET and to ascertain perceptions of the changes in symptom severity between timepoints."

"To gauge the severity of PEM, we asked ME/CFS volunteers to compare their current PEM with an episode in their day-to-day life during which they had severe PEM. Although the specific triggering event was different for each person, using the benchmark of ‘severe PEM’ created an individualised standard that could be compared across participants."

"Participants chose memorable events such as weddings and graduations. These memorable events created an internal standard for comparison that was salient to each participant’s experiences. [...]"

"VAS data were collected for 12 symptoms immediately following the QI and at the same six timepoints: physical fatigue, mental fatigue or mental fog, muscle aches, joint aches, headache, muscle weakness, light headedness, flu-like symptoms, sore throat, gastrointestinal symptoms, shortness of breath and sensitive to environment."

"Volunteers were provided a tablet and instructed ‘to place an ‘X’ on a line for each symptom to indicate how they felt RIGHT NOW’. (figure 1). Lines were anchored on the left and right side indicating ‘NOT AT ALL’ and ‘MOST EXTREME’."


[I think there are some good considerations and some less good considerations in that part. For now, hghlighted only the ones I find problematic with regard to potentially dismissing PEM while trying to capture it.]

 

I presume so.

The problem as ever is that unless you know why you are measuring something there is no way of knowing how you should be doing the measuring.

Why measure after a 'CPET' rather than just some standardised form of exertion.

Why call methods 'mixed' rather than just intelligently chosen for specific reasons.

To me this is boondoggling.

 

Plus, I realize I might not be representative but for me, having a 30-45 minutes conversation is more exhausting than doing a CPET and will cause immediate worsening of symptoms. Would feel overwhelmed by having to gauge my burden of twelve symptoms immediately after an interview that lasts more than 15-20 minutes.

I wonder if the study team took into consideration and asked participants whether the interview caused symptoms similar to some of the PEM symptoms?

 

That is too short a time for most people (maybe it's faster after max exertion).

 

In the Walitt et all deep phenotyping paper, she is also affiliated with the National Center for Complementary and Integrative Health (NCCIH). (More on NCCIH's aims in this thread.)

 

I have a scrambled brain, so I might make a mistake, but a quick skim makes me uneasy that this team is focussing on PEM perception.

In general it is an issue that different descriptions mean different things to patients. When they give how they feel a "4" that is not necessarily the same as their neighbour's 4. It's also relative to earlier states. No rocket science, and something to take into account when using subjective outcomes.

BUT

Walitt has a long track record of claiming ME is a disorder of subjective perception (which he calls an interoceptive disorder).
And the NCCIH (which Walitt is also closely affiliated with, and which Stussman is working for as well), whose aim it is to integrate complementary and conventional care, has recently declared "interoception research" as a top scientific priority for them. (More on that in this thread and this link.)

And then you have this study, which focuses on PEM perception and which makes the point that patients are not to be trusted when they report how they are doing.

and

Edited to add:

Like I said, I might be mistaken because of mush brain (I really need to log off), but atm, I do not like this. At all.