title: Comparison of distribution- and anchor-based approaches to infer changes in health-related quality of life of prostate cancer survivors.
abstract: OBJECTIVE
  To determine the minimal important difference (MID) in generic and prostate-specific health-related quality of life (HRQoL) using distribution- and anchor-based methods.
  
  
  METHODS
  Prospective cohort study of 602 newly diagnosed prostate cancer patients recruited from an urban academic hospital and a Veterans Administration hospital. Participants completed generic (SF-36) and prostate-specific HRQoL surveys at baseline and at 3, 6, 12, and 24 months posttreatment. Anchor-based and distribution-based methods were used to develop MID estimates. We compared the proportion of participants returning to baseline based on MID estimates from the two methods.
  
  
  RESULTS
  MID estimates derived from combining distribution- and anchor-based methods for the SF-36 subscales are physical function = 7, role physical = 14, role emotional = 12, vitality = 9, mental health = 6, social function = 9, bodily pain = 9, and general health = 8; and for the prostate-specific scales are urinary function = 8, bowel function = 7, sexual function = 8, urinary bother = 9, bowel bother = 8, and sexual bother = 11. Proportions of participants returning to baseline values corresponding to MID estimates from the two methods were comparable.
  
  
  CONCLUSIONS
  This is the first study to assess the MID for generic and prostate-specific HRQoL using anchor-based and distribution-based methods. Although variation exists in the MID estimates derived from these two methods, the recovery patterns corresponding to these estimates were comparable.
authors.affiliation: Department ofMedicine, Perelman School ofMedicine, University of Pennsylvania, 224, Ralston-Penn Center, 3615 Chestnut Street, Philadelphia, PA 19104-2676, USA. jravi@mail.med.upenn.edu
authors.forename: Ravishankar
authors.initials: R
authors.lastname: Jayadevappa
authors.forename: Stanley Bruce
authors.initials: SB
authors.lastname: Malkowicz
authors.forename: Marsha
authors.initials: M
authors.lastname: Wittink
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Wein
authors.forename: Sumedha
authors.initials: S
authors.lastname: Chhatre
mesh_terms: D003430:Cross-Sectional Studies; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010043:Outcome and Process Assessment, Health Care / Q000379:methods; D011471:Prostatic Neoplasms / Q000523:psychology / Q000534:rehabilitation / Q000628:therapy*; D019984:Quality Indicators, Health Care; D011787:Quality of Health Care; D011788:Quality of Life; D017741:Survivors / Q000523:psychology / Q000706:statistics & numerical data