title: Psychometric properties of the Fatigue Severity Scale in obese patients.
abstract: BACKGROUND
  The aim of this study was to examine the psychometric properties of the Fatigue Severity Scale (FSS) to verify whether this instrument is a valid tool to measure fatigue in obese patients, and to examine the prevalence of fatigue in obese patients.
  
  
  METHODS
  Before and after a three-week residential multidisciplinary integrated weight reduction program, 220 patients were asked to fill in the questionnaires: FSS, Profile of Mood States (Fatigue-Inertia subscale, POMS-Fatigue, and Vigor-Activity subscale, POMS-Vigor), and the Obesity-Related Well-Being (ORWELL-97). A subsample of 50 patients completed the questionnaire within two days.
  
  
  RESULTS
  The prevalence of fatigue using a cut-off value of 4 for the FSS score was 59%. Correlations were found between FSS and POMS-Fatigue and -Vigor scores (r=0.58 and 0.53, respectively). A relation was also found between FSS and ORWELL97 (r=0.52, 0.42 to 0.61). From the factorial analysis only 1 factor was extracted explaining 63% of variance, with factor loading values ranging from 0.71 (item 7) to 0.87 (item 6). Intraclass Correlation Coefficient was 0.89 (0.82 to 0.94), while the agreement as measured using the Standard Error of Measurement was 0.43 (0.36 to 0.54) corresponding to 13% (11 to 17%). Cronbach's alpha values ranged from 0.94 to 0.93. The internal responsiveness of FSS was comparable to the ORWELL97 (Standardized Response Mean=0.50 and 0.44, respectively).
  
  
  CONCLUSIONS
  Fatigue is an important and frequent symptom in obese patients and therefore should be routinely assessed in both research and clinical practice. This can be achieved using the FSS, which is a short, simple, valid and reliable tool for assessing and quantifying fatigue in obese patients.
authors.affiliation: Department of Research and Development, Schulthess Clinic, Lengghalde 2, 8008 Zurich, Switzerland. franco.impellizzeri@gmail.com
authors.forename: Franco M
authors.initials: FM
authors.lastname: Impellizzeri
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Agosti
authors.forename: Alessandra
authors.initials: A
authors.lastname: De Col
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sartorio
mesh_terms: D000339:Affect; D005221:Fatigue / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000523:psychology* / Q000628:therapy; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D061217:Weight Reduction Programs