Currently, the most important goal of MS disease modifying therapy is to prevent permanent disability.
Assessing disability outcomes in MS in clinical trials is a complex task. Most trials rely on a change in the Expanded Disability Status Scale (EDSS) score, observed over 3 or 6 months. The EDSS is a scale that takes several neurological functions into account (such as visual and motor functions) and assigns a score to each of them. When added up, this results in a final unique disability score.
In relapsing-remitting MS, accumulation of permanent disability is often obscured by short-lived neurological impairment caused by relapses. Therefore, delayed confirmation of newly acquired disability after a relapse is essential to distinguish irreversible progression from reversible disability associated with relapses.
A team of experts from Europe, America and Australia conducted an observational study on a very large group of people and suggested that longer disability confirmation periods, like 12 or 24 months, in the design of observational studies and some clinical trials, provide a more accurate evaluation of the disability progression in people with relapsing-remitting MS.
This study reemphasises the challenge of designing clinical trials in MS and confirms that, in some cases, longer observation is necessary for more reliable results.
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