Cautious Interpretation of Observational Data

To the Editor We read the article by Harding and colleagues¹ regarding escalation vs early intensive approaches in treating patients with multiple sclerosis (MS). We agree that treating MS early and aggressively to halt disease from the start sounds attractive. In fact, there are clinical trial data that find an association of an early vs delayed start of a higher-efficacy therapy with sustained relapse rate reductions.² However, there are limitations in interpreting observational data, especially in MS cohorts, that were not fully addressed in the article.