title: Short-Form 12 or Short-Form 36 to measure quality-of-life changes in dialysis patients?
abstract: BACKGROUND
  Short-Form 36 (SF-36) is a self-report health-related quality-of-life (HRQOL) questionnaire, widely used in dialysis patients. It consists of physical and mental component scores (PCS/MCS), ranging from 0 to 100. To improve efficiency, the Short-Form 12 (SF-12) was developed to reproduce PCS and MCS. We assessed the ability of SF-12 versus SF-36 to detect change over time, and the association of SF-12 versus SF-36 with short-term and long-term mortality in dialysis patients.
  
  
  METHODS
  Patients were selected from the Netherlands Cooperative Study on the Adequacy of Dialysis (N = 1379), a prospective follow-up study among incident dialysis patients (62.1% HD) who completed SF-36 measurements every 6 months. Changes in scores of SF-12 versus SF-36 were compared with intra-class correlation coefficients (ICCs). Subsequently, Bland-Altman plots were used to assess limits of agreement. Relationship with mortality was assessed with Cox models with and without a time-dependent variable, adjusted for age, sex, ethnicity, comorbidity and dialysis modality at baseline.
  
  
  RESULTS
  ICC for change in scores was 0.90 for MCS and 0.84 for PCS. Mean difference was -0.1 and 0.2, respectively, and limits of agreement were -8.3 to 8.4 for MCS change in scores and -8.8 to 9.2 for PCS. Adjusted hazard ratio's for mortality per 5 units increment were 0.87 (95% CI: 0.84-0.91) for MCS12, 0.87 (95% CI: 0.84-0.90) for MCS36, 0.79 (95% CI: 0.76-0.83) for PCS12 and 0.75 (95% CI: 0.71-0.78) for PCS36.
  
  
  CONCLUSIONS
  SF-12 can be used to detect change in HRQOL in cohort studies on dialysis patients. SF-12 and SF-36 were similarly associated with short-term and long-term mortality. However, the wide limits of agreement indicate that SF-12 and SF-36 can give different scores on the individual level, suggesting that for individual purposes SF-36 instead of SF-12 should be used.
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands Department of Nephrology, Sint Lucas Andreas Hospital, Amsterdam, The Netherlands.
authors.forename: Wim L
authors.initials: WL
authors.lastname: Loosman
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Tiny
authors.initials: T
authors.lastname: Hoekstra
authors.affiliation: Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Sandra
authors.initials: S
authors.lastname: van Dijk
authors.affiliation: Department of Epidemiology and Biostatistics and the EMGO Institute for Health, Care Research VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.affiliation: Department of Psychiatry, Sint Lucas Andreas Hospital/VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Adriaan
authors.initials: A
authors.lastname: Honig
authors.affiliation: Department of Nephrology, Sint Lucas Andreas Hospital, Amsterdam, The Netherlands.
authors.forename: Carl E H
authors.initials: CE
authors.lastname: Siegert
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
mesh_terms: D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006305:Health Status Indicators; D006306:Health Surveys; D006801:Humans; D007676:Kidney Failure, Chronic / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D009426:Netherlands; D011446:Prospective Studies; D011788:Quality of Life; D006435:Renal Dialysis / Q000401:mortality*; D011795:Surveys and Questionnaires; D015996:Survival Rate
keywords: SF-12; SF-36; dialysis; mortality; quality of life