OBJECTIVES: There are limited psychometric studies done using the Patient-Reported Outcomes Information System Short Form-Fatigue-Multiple Sclerosis 8a (PROMIS-Fatigue-MS-8a) questionnaire. This study validated the psychometric properties of the PROMIS-Fatigue-MS-8a questionnaire in participants with relapsing multiple sclerosis (RMS) enrolled in the phase 2 frexalimab study.

METHODS: PROMIS-Fatigue-MS-8a is an 8-item, patient-reported questionnaire using a 5-point Likert scale from 1 (never/not at all) to 5 (almost always/very much). It is converted to a T-score metric; higher scores indicate more fatigue. Psychometric and measurement properties of PROMIS-Fatigue-MS-8a were assessed using patient-reported outcome data from the 12-week, double-blind, randomised, placebo-controlled part of the frexalimab phase 2 study in adult participants with RMS (NCT04879628; N = 129). Analyses were performed using baseline and Week 12 data from pooled treatment arms.

RESULTS: The mean (standard deviation) baseline T-score was 52.7 (10.7). Item-to-item correlations were acceptable (i.e. between 0.4 and 0.9) for most of the items’ combinations, at both visits. Excellent internal consistency (Cronbach’s α = 0.96, at baseline and Week 12) and good test-retest reliability (intraclass correlation coefficient = 0.8, using Patient Global Impression of Change [PGIC-Fatigue] and Severity [PGIS-Fatigue]) were observed. Convergent validity was supported by high correlations (r >0.50) between the T-score and the physical and psychological domains of Multiple Sclerosis Impact Scale 29 (MSIS-29v2) and PGIS-Fatigue at baseline and Week 12. The construct validity was supported by significant differences in T-scores between PGIS-Fatigue groups at both baseline and Week 12 (p <0.001). Sensitivity to change was demonstrated at Week 12 by statistically significant differences in T-scores between groups defined by PGIS-Fatigue (p = 0.0006) and PGIC-Fatigue (p <0.0001).

CONCLUSIONS: This study demonstrated that PROMIS-Fatigue-MS-8a is reliable, valid and responsive to change, suggesting it as a fit-for-purpose instrument to evaluate fatigue in adult patients with RMS.