title: Factor analysis techniques for assessing sufficient unidimensionality of cancer related fatigue.
abstract: BACKGROUND
  Fatigue is the most common unrelieved symptom experienced by people with cancer. The purpose of this study was to examine whether cancer-related fatigue (CRF) can be summarized using a single score, that is, whether CRF is sufficiently unidimensional for measurement approaches that require or assume unidimensionality. We evaluated this question using factor analysis techniques including the theory-driven bi-factor model.
  
  
  METHODS
  Five hundred and fifty five cancer patients from the Chicago metropolitan area completed a 72-item fatigue item bank, covering a range of fatigue-related concerns including intensity, frequency and interference with physical, mental, and social activities. Dimensionality was assessed using exploratory and confirmatory factor analysis (CFA) techniques.
  
  
  RESULTS
  Exploratory factor analysis (EFA) techniques identified from 1 to 17 factors. The bi-factor model suggested that CRF was sufficiently unidimensional.
  
  
  CONCLUSIONS
  CRF can be considered sufficiently unidimensional for applications that require unidimensionality. One such application, item response theory (IRT), will facilitate the development of short-form and computer-adaptive testing. This may further enable practical and accurate clinical assessment of CRF.
authors.affiliation: Center on Outcomes, Research and Education, Evanston Northwestern Healthcare and Northwestern University, 1001 University Place, Suite 100, 60201 Evanston, IL, USA. js-lai@northwestern.edu [corrected]
authors.forename: Jin-Shei
authors.initials: JS
authors.lastname: Lai
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crane
authors.forename: David
authors.initials: D
authors.lastname: Cella
mesh_terms: D000368:Aged; D002641:Chicago; D005163:Factor Analysis, Statistical; D005221:Fatigue / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D011788:Quality of Life; D011795:Surveys and Questionnaires