Validation of the Pittsburgh Fatigability Scale in a mixed sample of adults with and without chronic conditions, 2019, Carlozzi et al

Paywall, https://journals.sagepub.com/doi/abs/10.1177/1359105319877448
Scihub, https://sci-hub.se/10.1177/1359105319877448

 

Interesting. I was tinkering with something a bit similar some time ago. It's based on asking about common activities. Overall it looks like a much better scale than some of the usual, more pragmatic and relevant.



Though it could still be much better. I think there would be more value out of removing time from the questions and using it instead as the score. So instead of "leisurely walk for 30 minutes" and rating how straining it is, I would frame it instead as "how long can you sustain X" and grade it from low to no effort all the way up to high-intensity aerobic exercise that even a healthy fit person could only sustain for a few minutes (like maximum speed sprinting).

I also think there is value in a similar scale that presents a hypothetical scenario of sustaining such activities for X hours per day and how long it could be sustained (1 day, several days, months, indefinitely, etc). Essentially to build a graded scale of ability to perform activities. The grading would essentially show a slope at which certain patient populations would drop off entirely. Any healthy person should be able to walk 1 hour per day every day for years on end. I can't even sustain it once. Dropping it down to 10 minutes I could maybe do it 2-3 days in a row but not without sacrificing other activities.

So this is a clear improvement on the usual as it uses common relatable activities. There is no arbitrariness to what the numbers mean so less room for inventing ridiculous notions like "within normal range" leading to "back to normal" in that arbitrary range as recovery. There is no interpretation to "can you walk for 1h?", it's an integral part of the human experience and very relatable.

I couldn't really go much further than a few notes I took for later, once my brain is able to actually work normally, but just for discussion's sake I'll paste them below. There is room for improvement but I think this here is the right model for a fatigability scale. Quite interesting to show fibromyalgia is more significant than MS, with the former being poo-pooed as whining and the other a very serious disease treated with great care.

 

Notes below from ideas I had a few weeks ago about a similar activity-based fatigability scale. I was in thinking mode about how we could do this ourselves but it's pretty obvious that this is a professional project so I left it at that. Just for discussion, but I think there is some value in the general concept of a common activity-based scale.

It's mostly rough notes but it's nice to see someone thinking along the same lines.

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Defining criteria for recovery and remission for ME.

The only reliable group that can create subjective criteria for those concepts are the patients themselves. Let’s do this.

Basically choose a set of common activities, rate how much you could do before vs how much you could do now and how much you would consider acceptable to self-manage.

Steps:

1. Define a group of common activities
2. Find from population estimates the amount of hours you could sustain each activity at an effortless pace just before getting sick and establish a pertinent scale based on patient experience

All the psychosocial research is built around self-report. This is on equal footing, in fact could be even better if we have a larger sample size.

Bonus point that it will highlight the enormous gap. I personally have lost about 95% capacity. Most people, including medical professionals, would assume 10-15% at most. That’s enormous.

Tier the activities from light to heavy. From enjoying a day at the beach to high-intensity training. It should go from trivial things that anyone who isn’t sick, say from a flu or food poisoning, is able to do without any effort all the way to activities that require significant effort. This creates a clear cut-off point past which ME patients cannot do.

3 tiers: light, moderate, high. All tiers should be sustainable by a healthy person should be able to sustain for:

• Light: 8h without burden and 16h with burden
• Moderate: 4h without burden and 8h with burden
• Heavy: 2h without burden and 4h with burden

Those activities should be rated as doable without payback, sustainable long-term without eating into overall capacity. Put another way: if it were a job that could sustain you very well financially, you could sustain it indefinitely.

To emphasize can’t vs. won’t, assume those are in a supporting context, where everything else aside, there is no added hardship such as the soul-crushing boredom of some work environments (good bosses, good coworkers, rewarding environment, great pay, etc).

Example activities (should be sorted from low to high effort):

1. Grocery shopping
2. Lawn mowing
3. Walking around a city
4. Cleaning the house
5. Cooking
6. Reading a book
7. Playing a challenging video game
8. Writing
9. Playing a musical instrument (learning works)
10. Talking to a friend
11. Playing baseball or cricket
12. Playing ice hockey
13. Shoveling snow or dirt
14. Playing a board game with friends
15. Driving a car
16. Skiing
17. Customer service
18. Talking on the phone
19. Answering a questionnaire
20. Watching a movie or TV show a home
21. At the cinema
22. Attending class on a light topic

Also need to answer how long in days you could continue doing this every day. Basically allow from once a year to all day. You could pleasantly do 4 hours of shopping but could likely do 12-16 if you had to.

How much would you want to do vs how much could you maximally do. What would be a burden vs. what wouldn’t.

Answer at your best, your most common and your worst.

We could ask the PACE participants (verified but anonymous) to answer this questionnaire and compare.

We can easily have controls, it’s an easy questionnaire. Facebook is pretty good for this.

We can do two arms: verified and self-reported. A batch coming from clinics run by specialists that confirm the diagnosis and another made of self-reported diagnoses for those who don’t have a useful GP.

We could add the option to name a physician that would be contacted to confirm the diagnosis, for those who have a useful GP that isn’t particularly known for treating ME, so we can expand the pool. And we could ask those GPs to refer their other patients if they have some.

 

It's good to see a study that recognises and tries to tease out the difference between fatigue and fatiguability (in FM and MS). Seems it isn't just an issue in ME.

The instrument itself needs tweaking for ME though. It's better than some others out there, for example relating to common activities and separating physical and cognitive effects are improvements, but there are weaknesses, too (for ME purposes).

One, there is a major ceiling effect. I would score 5 on all questions except the sitting quietly one, both on my best and my worst days. And sitting quietly is one of the items they propose removing from the scale - the other is watching TV - because in FM and MS it's not that fatiguing.

Two, it doesn't account for repeatability of an activity, nor for the delayed effect of PEM (it only looks at fatigue, presumably directly following the activity). I can sit up quietly for an hour once/day every day (during better periods) but twice/day will lead to PEM.

@rvallee has some excellent thoughts on that. Worth working on.

 

I agree it is a step forward.

However, I reiterate the above comments, it fails to distinguish between what can be done as a one off and what can be done regularly or repeatedly. It fails to take into account of our variability both in relation to PEM but also I suspect the cycles inherent in our condition for some people.

Given most of us are continuously balancing and prioritising between different activities, any meaningful measure needs also to look at the context of any activity being measured. For example some one prioritising social activity and excluding everything else from their schedule might report it less fatiguing than someone trying to fit it in with going for a daily walk.

Also individual activities do not occur in isolation, for example a social activity includes having reasonably clean clothes, an acceptable level of personal hygiene and either house cleaning or travel. It can be hard to get people to understand that going out for lunch may seem to be manageable, but the laundry, the shower and the travel added in may make it unattainable. (Aside, here it can be hard to get people to understand the distinction between the physical and the psychological, for example people mistake reluctance to be in public when not having showered for several weeks with psychological issues around socialising.)

This is particularly relevant if the scale is being used to measure a specific discrete intervention. Generally I find that if I focus on a specific intervention it may superficially result in an improvement in the targeted activity, but when looking at the context as a whole it becomes obvious that that improvement is a result of redirecting activity/energy rather than any overall improvement. So once the intervention is over, either the improvement disappears or in attempting to generalise it to other things, that can no longer be put off, I crash.

I have been playing in my mind how I could record my symptoms both to measure change taking into account variability but also how to help others understand. Here is what I had been thinking about:

Symptom A (or it could be in this context Activity A)

• Lowest rating in whole course of condition (inc. year)
• Highest rating in whole course of condition (inc. year)
  
• Lowest rating in current time period (week/month/quarter?)
• Highest rating in current time period (week/month/quarter?)
  
• Mean rating in current time period (week/month/quarter?), likely to be a guesstimate
  
• Rating now

Another issue in relation to this specific scale is floor and/or ceiling effects. I would only be able to respond Yes to having done the activity for a couple of items, because most would be beyond what I am currently able to do. So presumably on most items I would score myself 5. So this could hide a significant amount of change for an individual over time or significant variation between individuals.

 

They still haven't bothered to ask patients with specific illnesses (and different backgrounds) whether these questions are understandable/easily answered and relevant.