title: Meaning behind measurement: self-comparisons affect responses to health-related quality of life questionnaires.
abstract: OBJECTIVE
  The subjective nature of quality of life is particularly pertinent to the domain of health-related quality of life (HRQOL) research. The extent to which participants' responses are affected by subjective information and personal reference frames is unknown. This study investigated how an elderly population living with a chronic metabolic bone disorder evaluated self-reported quality of life.
  
  
  METHODS
  Participants (n = 1,331) in a multi-centre randomised controlled trial for the treatment of Paget's disease completed annual HRQOL questionnaires, including the SF-36, EQ-5D and HAQ. Supplementary questions were added to reveal implicit reference frames used when making HRQOL evaluations. Twenty-one participants (11 male, 10 female, aged 59-91 years) were interviewed retrospectively about their responses to the supplementary questions, using cognitive interviewing techniques and semi-structured topic guides.
  
  
  RESULTS
  The interviews revealed that participants used complex and interconnected reference frames to promote response shift when making quality of life evaluations. The choice of reference frame often reflected external factors unrelated to individual health. Many participants also stated that they were unclear whether to report general or disease-related HRQOL.
  
  
  CONCLUSIONS
  It is important, especially in clinical trials, to provide instructions clarifying whether 'quality of life' refers to disease-related HRQOL. Information on self-comparison reference frames is necessary for the interpretation of responses to questions about HRQOL.
authors.affiliation: Health Services Research Unit, University of Aberdeen, Aberdeen, AB25 22D, UK. c.robertson@abdn.ac.uk
authors.forename: Clare
authors.initials: C
authors.lastname: Robertson
authors.forename: Anne L
authors.initials: AL
authors.lastname: Langston
authors.forename: Sally
authors.initials: S
authors.lastname: Stapley
authors.forename: Elaine
authors.initials: E
authors.lastname: McColl
authors.forename: Marion K
authors.initials: MK
authors.lastname: Campbell
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
authors.forename: Graeme
authors.initials: G
authors.lastname: Maclennan
authors.forename: Peter L
authors.initials: PL
authors.lastname: Selby
authors.forename: Stuart H
authors.initials: SH
authors.lastname: Ralston
authors.forename: Peter M
authors.initials: PM
authors.lastname: Fayers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004164:Diphosphonates / Q000627:therapeutic use; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010001:Osteitis Deformans / Q000188:drug therapy / Q000503:physiopathology / Q000523:psychology*; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires; D006113:United Kingdom
chemical_list: D004164:Diphosphonates