Defining Activity-Based Subgroups in Multiple Sclerosis: A Review and Framework Proposal

This systematic review examines how multiple sclerosis is stratified into activity-based subgroups across clinical trials and regulatory guidance, identifying significant inconsistencies in terminology and definitions for 'active', 'highly active', and 'rapidly evolving severe' disease. The authors propose a standardized framework to improve consistency in treatment decision-making and health technology assessments.