title: A Rasch Analysis of Assessments of Morning and Evening Fatigue in Oncology Patients Using the Lee Fatigue Scale.
abstract: To accurately investigate diurnal variations in fatigue, a measure needs to be psychometrically sound and demonstrate stable item function in relationship to time of day. Rasch analysis is a modern psychometric approach that can be used to evaluate these characteristics.
  
  
  
  To evaluate, using Rasch analysis, the psychometric properties of the Lee Fatigue Scale (LFS) in a sample of oncology patients.
  
  
  
  The sample comprised 587 patients (mean age 57.3 ± 11.9 years, 80% women) undergoing chemotherapy for breast, gastrointestinal, gynecological, or lung cancer. Patients completed the 13-item LFS within 30 minutes of awakening (i.e., morning fatigue) and before going to bed (i.e., evening fatigue). Rasch analysis was used to assess validity and reliability.
  
  
  
  In initial analyses of differential item function, eight of the 13 items functioned differently depending on whether the LFS was completed in the morning or in the evening. Subsequent analyses were conducted separately for the morning and evening fatigue assessments. Nine of the morning fatigue items and 10 of the evening fatigue items demonstrated acceptable goodness-of-fit to the Rasch model. Principal components analyses indicated that both morning and evening assessments demonstrated unidimensionality. Person-separation indices indicated that both morning and evening fatigue scales were able to distinguish four distinct strata of fatigue severity.
  
  
  
  Excluding four items from the morning fatigue scale and three items from the evening fatigue scale improved the psychometric properties of the LFS for assessing diurnal variations in fatigue severity in oncology patients.
authors.affiliation: Department of Nursing Science, Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway; Department for Patient Safety and Development, Lovisenberg Diakonale Hospital, Oslo, Norway. Electronic address: anners.lerdal@medisin.uio.no.
authors.forename: Anners
authors.initials: A
authors.lastname: Lerdal
authors.affiliation: Division of Occupational Therapy, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden; Department of Occupational Therapy, University of Illinois, Chicago, Illinois, USA.
authors.forename: Anders
authors.initials: A
authors.lastname: Kottorp
authors.affiliation: Department for Patient Safety and Development, Lovisenberg Diakonale Hospital, Oslo, Norway; School of Nursing, University of California, San Francisco, California, USA.
authors.forename: Caryl
authors.initials: C
authors.lastname: Gay
authors.affiliation: Department of Oral and Maxillofacial Surgery, New York University, New York, New York, USA.
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Aouizerat
authors.affiliation: School of Nursing, University of California, San Francisco, California, USA.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Lee
authors.affiliation: School of Nursing, University of California, San Francisco, California, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Miaskowski
mesh_terms: D000368:Aged; D005221:Fatigue / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D017440:Photoperiod; D025341:Principal Component Analysis; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
keywords: Fatigue; Rasch analysis; cancer; diurnal pattern; psychometrics; quality of life; symptoms