Quantifying progression and delineating the onset of progression in multiple sclerosis (MS) have been subjects of considerable debate over many years. Particularly, as the current standard measures of disability, such as the expanded disability status scale (EDSS)1, lack linearity or responsiveness to change and do not define progression onset. Scalfari et al2 discuss the utility of time to secondary progressive MS as a potential outcome measure in MS and provide significant information on the factors that predict this milestone in MS disease course.

They raise several important and sometimes controversial points, none more contentious than the role of relapses in the development of progression. They find that early relapses within the first 2 years do significantly influence the timing of onset …