I used to think about the EDSS in the same way.
I think that the best way to look at it is as a descriptive tool, rather than a scale in the statistical sense.It almost meets the requirements for an interval scale, but it has an absolute zero. But, it has an absolute zero at each end. That makes it unusable for statistical analysis - hence “descriptive”. It does appear to have 5% steps, but if you take (say) EDSS 2.0 and 2.5, the difference is that of 1 or 2 Functional Systems being affected - now prove that the functional systems as defined by Kurtzke are all of equal importance.
My original objection was for EDSS10 (Dead from MS). We all know that MS is not actually a killer disease - WRONG.
If the MS starts to affect an individual’s brainstem, it can affect the autonomic nervous system, so maybe the heart stops pumping, or the lungs stop breathing, or the temperature regulation shuts off - and it was MS that was the killer for sure, only you cannot prove it.
The big problem with the EDSS is that some of the “Authorities” have latched onto it (without any real understanding) and it is used to decide on things that it was never intended for - like deciding whether someone is now SPMS and their supply of a DMD can now be cut off.
The same thing happens with other scales - the 25 Foot Timed Walk measures just that. However it can be used by the old PCTs (so probably the new CCGs) to decide if someone with a FES should still be funded.My CCG did introduce a new type of assessment form, and I will find out next week if they are still using it.
So, think about the EDSS as something that the clinicians have to use because the beancounters think that they understand it. And, actually, walking ability starts at EDSS 3.0.