In an earlier blog entry I already described one of the severity scales used for myalgic encephalomyelitis and why it is inadequate. Here, I want to briefly introduce another widely used scale and explain why it is also inadequate, and then present the one I wish patients, clinicians, and researchers would use more.
Probably the most widely used scale, besides the mild/moderate/severe/very severe categorizations, is the Bell scale.
A healthy person would score 100; a person who is completely bedbound and dependent on 24/7 care, 0. The Bell score is popular because it lets patients and clinicians describe a person’s functional capacity with one number.
The problem with the Bell score is that it mixes symptom severity, physical capacity, and cognitive capacity into one number. However, many people, especially toward the moderate to mild end, can be almost symptom-free when they pace well. And cognitive and physical capacity often don’t correlate. There are people who have trouble reading and understanding texts but can travel, even by plane. On the other hand, there are people who are housebound due to orthostatic intolerance or sensory intolerances but, as long as they remain horizontal, their cognitive capacity is not impaired too much.
What the Bell scale, and most other scales, also does not account for is PEM. Asking a person with myalgic encephalomyelitis “Can you do X?” is pointless. Many are capable of doing something if they prepare for it with, e.g. two days of bed rest, or if they are willing to accept the consequences of the activity in the form of PEM.
For example, many studies, but also disability assessments, use the 6-minute walk test as a proxy for physical capacity. Some people with myalgic encephalomyelitis would be able to complete that test easily within the target range for healthy people but would get PEM from it that forces them to spend the next two days in bed. Being able to do something in the moment doesn’t mean it does not have consequences.
This is part of the reason why I am a fan of the FUNCAP55 questionnaire. It doesn’t ask “Can you take a shower?”, but “What happens if you take a shower?” It asks about the consequences of activities of daily living.
And it does that for eight categories: personal hygiene, moving around, being upright, activities in the home, communication, activities outside the home, reactions to light and sound, and concentration. There is still a total score, but the subscores also take into account that people can be more severely affected in one aspect of life than another.
Plus, the questionnaire was developed and validated with thousands of patients. There is a peer-reviewed publication (1) that describes the development of the questionnaire in detail, and the process was sound. For most other questionnaires I know, the source was either lost, or one gets the impression that they were originally scribbled on a napkin based on vibes.
FUNCAP55 is also great for tracking illness progression, as it is more sensitive to smaller changes than, e.g. the Bell scale.
As my GP pointed out, FUNCAP55 may not be the best abbreviation ever because there is nothing fun about this illness, but hey, no scale is perfect.
In my opinion, at this point FUNCAP55 and its shortened version, FUNCAP27 is the best we have, and I wish more patients would use it. It can only become widespread if we use it and, instead of asking “What Bell are you?”, ask “What’s your FUNCAP55 score?”
(1) Sommerfelt, K. et. al. 2024, Journal of Clinical Medicine, 13(12), 3486