The search for responsive clinical endpoints in primary progressive multiple sclerosis.

OBJECTIVE

To determine whether in primary progressive multiple sclerosis (PPMS) combining scores of Expanded Disability Status Scale (EDSS) with data from Timed 25-Foot Walk (T25FW) and 9-Hole Peg Test (9HPT) would produce a clinical endpoint that has a higher event rate than EDSS alone.

METHODS

In a group of 161 PPMS patients, EDSS, T25FW, and 9HPT were performed at three time points over 2 years. We calculated how many patients showed clinically meaningful deterioration (or improvement) on individual and combined scales. We defined improvements on one scale with deterioration on the other as "opposing changes." We investigated the possible effect of baseline disability on the definition of our endpoint by dividing the population into two subsets of patients determined by baseline EDSS level.

RESULTS

On individual scales, event rates were highest on T25FW: 34% and 46% 1 year and 2 years after baseline. On a combination of two scales, at 1 year the event rate was highest on T25FW/9HPT (46%; with a high rate of opposing changes) and at 2 years on T25FW/EDSS (57%; with a lower rate of opposing changes). In both subsets, event rates were highest on T25FW and (at 2 years) on the combination of T25FW/EDSS.

CONCLUSIONS

T25FW has the highest event rate as a single scale, independent of baseline disability level. A term of 2 years turned out to be more meaningful to observe than 1 year. "Worsening on either T25FW or EDSS" is the most appropriate composite endpoint in this patient group.