Treating to target in multiple sclerosis: Do we know how to measure whether we hit it?

Background And Purpose The rapidly evolving landscape of effective treatment options in multiple sclerosis has led to a shift of treatment objectives towards a treat-to-target approach aiming to suppress disease activity below the level of detectability early during the disease. To enable treat-to-target, a thorough reappraisal of available outcome measures with respect to their ability in this regard is required.Methods To that end, we conducted a comprehensive systematic literature review of more than 1000 studies using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 methodology focusing on underlying evidence as well as utility and implementability in clinical practice.Results From there, we propose a set of measurable outcomes for everyday routine clinical practice as well as advanced/aspirational measurables requiring additional resources. We also outline remaining knowledge/technology gaps that need to be overcome to enable a treat-to-target approach.Conclusions This work provides the basis for an evidence-based definition of outcome targets for relevant stakeholders and regulatory authorities.