Part 2 · The course
Measuring disability: EDSS
The Expanded Disability Status Scale runs from 0 (normal exam) to 10 in half-steps. Climb the staircase to see what each step means, try a teaching calculator, and see when worsening counts as confirmed.
Walking and care anchors from 4.0 upward as published. For 1.0–3.5 only the published general description is shown (increasing signs in the functional systems, fully ambulatory); the exact grade rules for each half-step are not reproduced here. Figures are schematic. 90,109,265
Try it: a teaching calculator
A teaching tool, not a clinical score. A real EDSS comes from a full neurological examination by a trained examiner, who grades each functional system and applies Kurtzke's detailed rules. This simplified version does not reproduce those rules: it uses only the published walking and care anchors, and places any examination findings with full walking in the 1.0–3.5 range. Even trained raters disagree: reported inter-rater kappa is 0.32–0.76 for the total score and 0.23–0.58 for individual functional systems. 313
Functional systems with signs on examination (tick any; simplified, no grades)
When does worsening count? Confirmed disability progression
In trials, confirmed disability accumulation is typically an EDSS rise of at least 1.0 point from a baseline of 5.5 or less, or at least 0.5 point from a baseline above 5.5, that is still there at a visit 12 or 24 weeks later. Composite definitions add a 20% or greater worsening on the timed 25-foot walk or the 9-hole peg test. Watch one person's visits below: a short-lived rise and a lasting one. 235
Schematic visits for one illustrative person. The bars are published MSBase figures. 230
Beyond EDSS: other measures
MS Functional Composite
Built in 1999 from three timed tests: the Timed 25-Foot Walk (legs), the 9-Hole Peg Test (arms) and the PASAT (cognition), combined as a z-score. Change over one year predicted later change in EDSS, which suggests it is more sensitive to change. Its main limitations are learning effects and the z-score scoring. 105,313
Timed walk and peg test
The Timed 25-Foot Walk and the 9-Hole Peg Test are used alone too. In trial composites, a 20% or greater worsening on either counts toward confirmed disability progression. Walking speed is also how fampridine response was measured: 35% timed-walk responders vs 8% on placebo. 172,235
Symbol Digit Modalities Test
Measures processing speed. A change of about 4 points or 10% has been proposed as clinically meaningful. It is brief, reliable and sensitive enough to monitor cognition, including during acute disease activity. 28,29
Why EDSS is criticised
It is ordinal, not a ruler: the lower range rests on the examination, 4–6 depends heavily on walking, and above 6 it measures handicap. Variability between raters is greatest at 1.0–3.5. Across 48 progression definitions in MSBase, concordance was only 17.3%, and 11–34% of progression events regressed within 5 years. 230,313