Measurement Characteristics and Clinical Utility of the Modified Fatigue Impact Scale in Individuals With Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease affecting approximately 2.3 million people worldwide.¹ Fatigue occurs in approximately 80% of individuals with MS.² The Modified Fatigue Impact Scale (MFIS) is a modified form of the Fatigue Impact Scale,³ based on items derived from interviews with patients with MS concerning how fatigue affects their lives. The full-length MFIS has 21 items, whereas the short version has 5 items. The full-length version generates 3 subscales (physical, cognitive, and psychosocial functioning), which assess the perceived effect of fatigue during the last 4 weeks.⁴ Participants rate the MFIS on a 5-point Likert scale from 0 (never) to 4 (almost always). Total scores range from 0 to 84; for the subscale scores, the physical subscale ranges from 0 to 36, the cognitive subscale ranges from 0 to 40, and the psychosocial functioning subscale ranges from 0 to 8. The scores range from 0 to 20 for the 5-item version. Higher numbers indicate greater fatigue. The scale has been shown to have adequate to excellent concurrent and content validity^{4.,  5.,  6.,  7.} and excellent test-retest reliability in patients with MS.^{4.,  5.} Rasch analysis revealed that the 21-item scale was found to contain a physical and cognitive dimension (the original 2 social items were found to be part of the physical dimension).^{4.,  5.} Additionally, the MFIS has been found to show change after a 4-week intervention.^{4.,  5.} The MFIS can be administered and scored in 5 to 10 minutes, making it a clinically useful and low-burden instrument. The MFIS is free to use, and has been recommended by the Neurology Section of the American Physical Therapy Association's Multiple Sclerosis Taskforce.