Is it time to use observational data to estimate treatment effectiveness in multiple sclerosis?

There is growing interest in the use of observational data to estimate treatment effects in chronic diseases such as multiple sclerosis (MS). While randomized, controlled trials (RCTs) have long been viewed as the gold standard for estimating treatment effects, there are instances in which they are unethical or impractical.1 Even if an RCT is feasible, interest often focuses on estimating treatment effects in real-world settings, outside the tightly controlled confines of an RCT. Observational studies may be especially valuable for answering long-term questions in MS such as the long-term impact of currently available disease modifying drugs (DMDs) in preventing unremitting disability progression.2 Open-label extensions of RCTs3,4 also tried to assess this issue but their initial methodologic rigor seems to be lost during the extension phase.5 In this issue of Neurology ®, Brown et al.6 report on the use of a large database to analyze the effectiveness of a DMD program in delaying disability progression in a population-based cohort of 590 patients with relapsing-onset definite MS in Nova Scotia. DMD effectiveness was examined by comparing individuals' estimated annual changes in Expanded Disability Status …