title: A 7-item version of the fatigue severity scale has better psychometric properties among HIV-infected adults: an application of a Rasch model.
abstract: OBJECTIVE
  To examine the psychometric properties of the 9-item Fatigue Severity Scale (FSS) using a Rasch model application.
  
  
  METHODS
  A convenience sample of HIV-infected adults was recruited, and a subset of the sample was assessed at 6-month intervals for 2 years. Socio-demographic, clinical, and symptom data were collected by self-report questionnaires. CD4 T-cell count and viral load measures were obtained from medical records. The Rasch analysis included 316 participants with 698 valid questionnaires.
  
  
  RESULTS
  FSS item 2 did not advanced monotonically, and items 1 and 2 did not show acceptable goodness-of-fit to the Rasch model. A reduced FSS 7-item version demonstrated acceptable goodness-of-fit and explained 61.2% of the total variance in the scale. In the FSS-7 item version, no uniform Differential Item Functioning was found in relation to time of evaluation or to any of the socio-demographic or clinical variables.
  
  
  CONCLUSIONS
  This study demonstrated that the FSS-7 has better psychometric properties than the FSS-9 in this HIV sample and that responses to the different items are comparable over time and unrelated to socio-demographic and clinical variables.
authors.affiliation: Lovisenberg Deaconal University College, Lovisenbergveien 15b, 0456, Oslo, Norway. Anners.Lerdal@ldh.no
authors.forename: Anners
authors.initials: A
authors.lastname: Lerdal
authors.forename: Anders
authors.initials: A
authors.lastname: Kottorp
authors.forename: Caryl
authors.initials: C
authors.lastname: Gay
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Aouizerat
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Portillo
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D005221:Fatigue / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006679:HIV Seropositivity / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D011788:Quality of Life; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult