title: Estimating clinically significant differences in quality of life outcomes.
abstract: OBJECTIVE
  This report extracts important considerations for determining and applying clinically significant differences in quality of life (QOL) measures from six published articles written by 30 international experts, in the field of QOL assessment and evaluation. The original six articles were presented at the Symposium on Clinical Significance of Quality of Life Measures in Cancer Patients at the Mayo Clinic in April 2002 and subsequently were published in Mayo Clinic Proceedings.
  
  
  RESULTS
  Specific examples and formulas are given for anchor-based methods, as well as distribution-based methods that correspond to known or relevant anchors to determine important differences in QOL measures. Important prerequisites for clinical significance associated with instrument selection, responsiveness, and the reporting of QOL trial results are provided. We also discuss estimating the number needed to treat (NNT) relative to clinically significant thresholds. Finally, we provide a rationale for applying group-derived standards to individual assessments.
  
  
  CONCLUSIONS
  While no single method for determining clinical significance is unilaterally endorsed, the investigation and full reporting of multiple methods for establishing clinically significant change levels for a QOL measure, and greater direct involvement of clinicians in clinical significance studies are strongly encouraged.
authors.affiliation: Saint Louis University, St Louis, MO 63103, USA. wyewichk@slu.edu
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Wyrwich
authors.forename: Monika
authors.initials: M
authors.lastname: Bullinger
authors.forename: Neil
authors.initials: N
authors.lastname: Aaronson
authors.forename: Ron D
authors.initials: RD
authors.lastname: Hays
authors.forename: Donald L
authors.initials: DL
authors.lastname: Patrick
authors.forename: Tara
authors.initials: T
authors.lastname: Symonds
mesh_terms: D003430:Cross-Sectional Studies; D006801:Humans; D009369:Neoplasms / Q000503:physiopathology* / Q000523:psychology; D015588:Observer Variation; D017063:Outcome Assessment, Health Care; D011788:Quality of Life