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Modified Fatigue Impact Scale (MFIS)
Please visit this website for more information about the instrument: Modified Fatigue Impact Scale (MFIS)
Supplemental - Highly Recommended: Mitochondrial Disease (Mito)
Recommendations for use: Indicated for studies requiring a measure of fatigue.
Supplemental: Amyotrophic Lateral Sclerosis (ALS), Friedreich's Ataxia (FA), Multiple Sclerosis (MS)
Exploratory: Myalgic encephalomyelitis/Chronic fatigue syndrome (ME/CFS)
Short Description of Instrument
The Modified Fatigue Impact Scale (MFIS) is a modified version of the 40-item Fatigue Impact Scale (FIS) which was developed to assess the effects of fatigue on quality of life in patients with MS (Fisk et al, 1994a,b; Larson, 2013). The MFIS is one of the components of the Multiple Sclerosis Quality of Life Inventory (MSQLI) and the full-length version consists of 21-items; the abbreviated version consists of 5-items. This instrument provides an assessment of the effects of fatigue in terms of physical, cognitive, and psychosocial functioning. The abbreviated version can be used if time is limited but the full-length version has the advantage of generating subscales (National Multiple Sclerosis Society, n.d.).
Comments/Special Instructions
The MFIS-21 has three subscales, physical, cognitive and psychosocial. The physical and cognitive subscales are comprised of nine (#4, #6, #7, #10, #13, #14, #17, #20, #21) and 10 (#1, #2, #3, #5, #11, #12, #15, #16, #18, #19) questions, respectively. Questions #8 and #9 comprise the psychosocial subscale.
The MFIS-5, five items include two items from the physical subscale (#10 and #17), two items from the cognitive subscale (#1 and #19) and one item from the psychosocial subscale (#9). (Meca-Lallana et al., 2019)
Scoring and Psychometric Properties
Scoring: The total score is the sum of the scores for the 21 items. Subscale scores are the sum of the scores for items in the subscale. Users should refer to the MSQLI User's Manual for detailed scoring instructions for both the full length 21-item MFIS and abbreviated 5-item version. Each item is scored between 0 (never) and 4 (almost always). Total score varies between 0-84 and are obtained by adding scores for each of the sub-scales. The sub-scales scores are 0-36 (physical), 0-40 (cognitive) and 0-8 (psychosocial).
Psychometric Properties:
MS Psychometric Properties: NOTE: Limited data on psychometric properties in North American MS populations are available. Summary of demonstrated properties below includes data from both N. American and European MS studies.
The full-length version of the MFIS has a Cronbach's alpha of .81 while the short form has an alpha of .80. (Fisk et al., 1994b)  Fisk et al. (1994b) found the FIS to be sensitive in discriminating the effects of fatigue among MS from those of patients with chronic fatigue syndrome and essential hypertension. (Ritvo et al., 1997)
Reliability: Cronbach's alpha [MSQLI field test population]: Total MFIS = .81, Cognitive subscale = .95, Physical subscale = .91, psychosocial subscale = .81, and abbreviated version = .80; Cronbach's alpha [four-country European study (Kos et al., 2005)]: Total MFIS = .92, Cognitive subscale = .92, Physical subscale = .88, psychosocial subscale = .65; Reproducibility: ICC = .91 (Kos et al., 2005); Convergent Validity: MFIS correlates with the Fatigue Severity Scale: Spearman r =.68, p<.0001 in an RRMS predominate Spanish population (Téllez et al., 2005); r =.66, p<.0001 in a four-country European study (Kos et al., 2005); Kendall's Tau-b = 0.729, Dutch MFIS. (Kos et al., 2003) Divergent Validity: Does not diverge from Beck Depression Inventory (Spearman r = .7, p<.0001); divergence from EDSS (r = .30, p<.0001; r = 0.15, p =.02 after adjusting for BDI) (Téllez et al., 2005) Sensitivity: Dutch MFIS sensitive to change (z = -3.401, p =. 001) following a four-week rehabilitation program; no floor or ceiling effect detected.
Strengths: The MFIS 21-item scale is easy to administer and has high face validity for patients because it focuses on the effect of fatigue on daily activities. Subscales allow for research on specific areas of function, but they are highly correlated with each other.
Weaknesses: A limitation of the MFIS is that the assessment cannot distinguish between sleepiness and alertness with respect to impact of fatigue. (Larson et al., 2013)
Strengths: This scale is free to use. It might be useful for comparison with people with MS. This form is part of a modular instrument MSQLI, which contains a free version of the health status (SF-36), perceived deficits questionnaire (PDQ) and other questionnaires, some of them could be useful in ME/CFS, though others would be very specific to MS. The subscales may be useful to investigators interested in testing hypotheses concerning these different areas of function.
Weaknesses: This scale has not been validated in ME/CFS. It measures the impact and not the severity of fatigue and there are no questions on post-exertional malaise. This scale could be potentially used alongside a scale exploring severity.
Mitochondrial Disease-Specific:
Strengths: It is clearly defined for impact of fatigue as opposed to simply degree of fatigue. Currently used in trials. MFIS has well documented use across groups. Easy to administer, low burden. Has been validated but not published.
Weaknesses: Scale has ceiling effects.
Key Reference:
Ritvo PG, Fischer JS, Miller DM, Andrews H, Paty D, LaRocca NG. Modified Fatigue Impact Scale (MFIS). In: Multiple Sclerosis Quality of Life Inventory: A User's Manual. New York, NY: National Multiple Sclerosis Society;1997, p.23. Retrieved 15Oct2024 from
Additional References:
Fisk JD, Pontefract A, Ritvo PG, Archibald CJ, Murray TJ. The impact of fatigue on patients with multiple sclerosis. Can J Neurol Sci. 1994a Feb;21(1):9-14.
Fisk JD, Ritvo PG, Ross L, Haase DA, Marrie TJ, Schlech WF. Measuring the functional impact of fatigue: initial validation of the fatigue impact scale. Clin Infect Dis. 1994b;18 Suppl 1:S79-S83.
Kos D, Kerckhofs E, Carrea I, Verza R, Ramos M, Jansa J. Evaluation of the Modified Fatigue Impact Scale in four different European countries. Mult Scler. 2005 Feb;11(1):76-80.
Kos D, Kerckhofs E, Nagels G, D'Hooghe BD, Duquet W, Duportail M, Ketelaer P. Assessing fatigue in multiple sclerosis: Dutch modified fatigue impact scale. Acta Neurol Belg. 2003 Dec;103(4):185-91.
Larson RD. Psychometric properties of the modified fatigue impact scale. Int J MS Care. 2013 Spring;15(1):15-20.
Mathiowetz V. Test-retest reliability and convergent validity of the Fatigue Impact Scale for persons with multiple sclerosis. Am J Occup Ther. 2003 Jul-Aug;57(4):389-95.
Meca-Lallana V, Brañas-Pampillón M, Higueras Y, Candeliere-Merlicco A, Aladro-Benito Y, Rodríguez-De la Fuente O, Salas-Alonso E, Maurino J, Ballesteros J. Assessing fatigue in multiple sclerosis: Psychometric properties of the five-item Modified Fatigue Impact Scale (MFIS-5). Mult Scler J Exp Transl Clin. 2019 Nov 9;5(4):2055217319887987.
Multiple Sclerosis Council for Clinical Practice Guidelines. Fatigue and Multiple Sclerosis: Evidence Based Management Strategies for Fatigue in Multiple Sclerosis. Washington, DC: Paralyzed Veterans of America; 1998. Retrieved 15Mar2024 from:
Téllez N, Río J, Tintoré M, Nos C, Galán I, Montalban X. Does the Modified Fatigue Impact Scale offer a more comprehensive assessment of fatigue in MS? Mult Scler. 2005 Apr;11(2):198-202.
Whitehead L. The measurement of fatigue in chronic illness: a systematic review of unidimensional and multidimensional fatigue measures. J Pain Symptom Manage. 2009 Jan;37(1):107-28.
ALS-Specific References:
Fischer JS, Rudick RA, Cutter GR, Reingold SC. The Multiple Sclerosis Functional Composite Measure (MSFC): an integrated approach to MS clinical outcome assessment. National MS Society Clinical Outcomes Assessment Task Force. Mult Scler. 1999 Aug;5(4):244-50.
Fisk JD, Pontefract A, Ritvo PG, Archibald CJ, Murray TJ. The impact of fatigue on patients with multiple sclerosis. Can J Neurol Sci. 1994a Feb;21(1):9-14.
Mitochondrial Disease-Specific Reference:
Gorman GS, Elson JL, Newman J, Payne B, McFarland R, Newton JL, Turnbull DM. Perceived fatigue is highly prevalent and debilitating in patients with mitochondrial disease. Neuromuscul Disord. 2015 Jul;25(7):563-6.
Document last updated March 2024