Systematic review of outcome measures in facioscapulohumeral dystrophy (FSHD): validated, usable, and feasible tools for assessing function, performance, and strength.

Facioscapulohumeral dystrophy (FSHD) is a dominantly inherited muscle-wasting condition with no approved therapies. Symptom variability complicates clinical evaluation, and despite the necessity of function-based measures to bridge research and real-world outcomes, no international consensus on a core assessment set exists. This systematic review evaluated the psychometric properties, feasibility, and comprehensiveness of published function-based outcome measures in FSHD, to help guide late-phase trials, and clinical practice. A systematic search of six databases with a data cut in January 2026 identified 366 studies and 51 outcome measures, which were appraised using the COSMIN framework. The results showed that while the FSHD Clinical Score, Clinical Severity Score, and 6-minute walk test are the most frequently utilised, no measure achieved higher than a 'Moderate' rating. Most supporting evidence remains 'Low,' with critical gaps identified for wheelchair users and paediatric populations. Digital outcome measures showed promise for improving responsiveness and enabling remote assessment.Our systematic review highlights an urgent need for a consensus-based approach to harmonize data together with international efforts such as MOVE/RESOLVE-FSHD providing direct support to upcoming initiatives like ENMC-FSHD-outcomes- workshop and the PaLaDIn project. Such efforts will allow researchers to enhance real-world evidence synthesis and improve success of future clinical trials.