title: Outcome measurement in functional somatic syndromes: SF-36 summary scores and some scales were not valid.
abstract: OBJECTIVE
  This study aimed to test the validity of the 36-item Short-Form Health Survey (SF-36) scales and summaries in patients with severe functional somatic syndromes (FSS), such as fibromyalgia and irritable bowel syndrome.
  
  
  METHODS
  One hundred twenty patients with severe FSS enrolled in a randomized controlled trial filled in the SF-36 questionnaire. We tested for data quality, central scaling assumptions, and agreement with the conceptual model.
  
  
  RESULTS
  Most SF-36 scales were found to be valid; however, three scales (role physical, role emotional, and general health) did not satisfy predefined criteria for construct validity, internal consistency, or targeting to the sample. The correlations between SF-36 scales differed considerably from those reported in the general population. As a consequence, the SF-36 summaries, physical component summary (PCS) and mental component summary (MCS), did not accurately reflect their underlying scales and were negatively correlated (r=-0.46, 95% CI [-0.60 to -0.31]).
  
  
  CONCLUSIONS
  Although the SF-36 is a valuable instrument to assess perceived health in patients with severe FSS, there are problems with some of the scales and with the scoring procedure of the summaries. The SF-36 PCS may, therefore, not accurately measure the physical health status of these patients. Alternative summary measures are needed.
authors.affiliation: The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Noerrebrogade 44, 8000 Aarhus C, Denmark. andreas.schroeder@aarhus.rm.dk
authors.forename: Andreas
authors.initials: A
authors.lastname: Schröder
authors.forename: Eva
authors.initials: E
authors.lastname: Oernboel
authors.forename: Rasmus W
authors.initials: RW
authors.lastname: Licht
authors.forename: Michael
authors.initials: M
authors.lastname: Sharpe
authors.forename: Per
authors.initials: P
authors.lastname: Fink
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis; D006306:Health Surveys; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis; D008297:Male; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012107:Research Design; D012494:Sampling Studies; D012647:Self-Assessment; D012720:Severity of Illness Index; D018434:Sickness Impact Profile; D013001:Somatoform Disorders / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D011795:Surveys and Questionnaires; D013577:Syndrome