title: Measuring fatigue in Parkinson's disease: a psychometric study of two brief generic fatigue questionnaires.
abstract: This study evaluated and compared the measurement properties of the 13-item Functional Assessment of Chronic Illness Therapy-Fatigue Scale (FACIT-F) and the 9-item Fatigue Severity Scale (FSS) in 118 consecutive Parkinson's disease (PD) patients, using traditional and Rasch measurement methodologies. Both questionnaires exhibited excellent data quality and reliability (coefficient alpha>or=0.9), and acceptable rating scale functionality, and both discriminated between fatigued and nonfatigued patients. Factor and Rasch analyses provided general support for unidimensionality of both FACIT-F and FSS, although they do not appear to measure identical aspects of fatigue. No signs of differential item functioning (DIF) were found for the FACIT-F, whereas potential age DIF was detected for two FSS items. These results support the measurement validity of both questionnaires in PD, although the FACIT-F displayed better measurement precision and modest psychometric advantages over the FSS. Availability of psychometrically sound fatigue measures that are applicable across disorders provides a sound basis for advancing the understanding of this common and distressing complaint.
authors.affiliation: Department of Health Sciences, Lund University, Sweden. Peter.Hagell@med.lu.se
authors.forename: Peter
authors.initials: P
authors.lastname: Hagell
authors.forename: Arja
authors.initials: A
authors.lastname: Höglund
authors.forename: Jan
authors.initials: J
authors.lastname: Reimer
authors.forename: Brita
authors.initials: B
authors.lastname: Eriksson
authors.forename: Ingmari
authors.initials: I
authors.lastname: Knutsson
authors.forename: Håkan
authors.initials: H
authors.lastname: Widner
authors.forename: David
authors.initials: D
authors.lastname: Cella
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000523:psychology*; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires