title: Validation of the Modified Fatigue Impact Scale in Parkinson's disease.
abstract: BACKGROUND
  Fatigue is a common symptom in Parkinson's disease (PD); however, a multidimensional scale that measures the impact of fatigue on functioning has yet to be validated in this population. The aim of this study was to examine the validity of the Modified Fatigue Impact Scale (MFIS), a self-report measure that assesses the effects of fatigue on physical, cognitive, and psychosocial functioning, in a sample of nondemented PD patients.
  
  
  METHODS
  PD patients (N = 100) completed the MFIS, the Positive and Negative Affect Schedule (PANAS-X), and several additional measures of psychosocial, cognitive, and motor functioning. A Principal Component Analysis (PCA) and item analysis using Cronbach's alpha were conducted to determine structural validity and internal consistency of the MFIS. Correlational analyses were performed between the MFIS and the PANAS-X fatigue subscale to evaluate convergent validity and between the MFIS and measures of depression, anxiety, apathy, and disease-related symptoms to determine divergent validity.
  
  
  RESULTS
  The PCA identified two viable MFIS subscales: a cognitive subscale and a combination of the original scale's physical and psychosocial subscales as one factor. Item analysis revealed high internal consistency of all 21 items and the items within the two subscales. The MFIS had strong convergent validity with the PANAS-X fatigue subscale and adequate divergent validity with measures of disease stage, motor function, and cognition.
  
  
  CONCLUSIONS
  Overall, this study demonstrates that the MFIS is a valid multidimensional measure that can be used to evaluate the impact of fatigue on cognitive and physical/social functioning in PD patients without dementia.
authors.affiliation: Research Service, VA San Diego Healthcare System, San Diego, CA 92161, USA. dschiehser@ucsd.edu
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Schiehser
authors.forename: Catherine R
authors.initials: CR
authors.lastname: Ayers
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lessig
authors.forename: David S
authors.initials: DS
authors.lastname: Song
authors.forename: J Vincent
authors.initials: JV
authors.lastname: Filoteo
mesh_terms: D000368:Aged; D004185:Disability Evaluation; D005221:Fatigue / Q000209:etiology* / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D010300:Parkinson Disease / Q000150:complications*; D025341:Principal Component Analysis; D012720:Severity of Illness Index