Results from Patient Interviews on Fatigue in Progressive Multiple Sclerosis and Evaluation of Fatigue Patient-Reported Outcome (PRO) Instruments.

Introduction: Fatigue is one of the most common and debilitating symptoms of multiple sclerosis (MS) but is challenging to assess and has not been comprehensively characterized in patients with progressive MS. This study aimed to (1) obtain qualitative evidence from patients with progressive MS to characterize MS-related fatigue concepts and their impacts on health-related quality of life (HRQoL), and (2) evaluate the conceptual frameworks of existing MS-specific fatigue patient-reported outcome (PRO) instruments using study data to determine the most suitable PRO instrument in this population.

Methods: Qualitative interviews were conducted with 30 US participants with confirmed progressive MS and fatigue in the last 6 months to assess their MS-related fatigue. Data were compared with concepts in existing PRO instruments to evaluate their relevance in progressive MS.

Results: Physical and mental concepts of fatigue were identified and characterized distinctly from patients with progressive MS. Most patients characterized fatigue as occurring daily and lasting several hours, with negative impacts on HRQoL. Concept mapping to existing MS-specific fatigue PRO instruments supported the Fatigue Severity Impact Questionnaire-Relapsing Multiple Sclerosis (FSIQ-RMS) as the most suitable existing option for assessing fatigue in patients with progressive MS, as it separates physical and mental aspects of fatigue and includes every highly endorsed concept reported by the interviewed patients.

Conclusions: This qualitative study identified meaningful physical and mental fatigue concepts in patients with progressive MS and preliminarily supports the use of the FSIQ-RMS for this population. More research is needed to fully validate this instrument for progressive MS.