title: Level of agreement between patient-reported EQ-5D responses and EQ-5D responses mapped from the SF-12 in an injury population.
abstract: BACKGROUND
  Comparing health-related quality of life (HRQL) outcomes between studies is difficult due to the wide variety of instruments used. Comparing study outcomes and facilitating pooled data analyses requires valid "crosswalks" between HRQL instruments. Algorithms exist to map 12-item Short Form Health Survey (SF-12) responses to EQ-5D item responses and preference weights, but none have been validated in populations where disability is prevalent, such as injury.
  
  
  METHODS
  Data were extracted from the Validating and Improving injury Burden Estimates Study (Injury-VIBES) for 10,166 adult, hospitalized trauma patients, with both the three-level EQ-5D (EQ-5D-3L) and SF-12 data responses at six and 12-months postinjury. Agreement between actual (patient-reported) and estimated (mapped from SF-12) EQ-5D-3L item responses and preference weights was assessed using Kappa, Prevalence-Adjusted Bias-Adjusted Kappa statistics and Bland-Altman plots.
  
  
  RESULTS
  Moderate agreement was observed for usual activities, pain/discomfort, and anxiety/depression. Agreement was substantial for mobility and self-care items. The mean differences in preference weights were -0.024 and -0.012 at six and 12 months (p < 0.001), respectively. The Bland-Altman plot limits of agreement were large compared to the range of valid preference weight values (-0.56 to 1.00). Estimated EQ-5D-3L responses under-reported disability for all items except pain/discomfort.
  
  
  CONCLUSIONS
  Caution should be taken when using EQ-5D-3L responses mapped from the SF-12 to describe patient outcomes or when undertaking economic evaluation, due to the underestimation of disability associated with mapped values. The findings from this study could be used to adjust expected EQ-5D-3L preference weights when estimated from SF-12 item responses when combining data from studies that use either instrument.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia ; Centre for Improvement of Population Health through E-records Research, Swansea University, Swansea, UK.
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Gabbe
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: McDermott
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors.forename: Pam M
authors.initials: PM
authors.lastname: Simpson
authors.affiliation: Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand ; School of Health and Social Services, Massey University, Palmerston North, New Zealand.
authors.forename: Sarah
authors.initials: S
authors.lastname: Derrett
authors.affiliation: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand.
authors.forename: Shanthi
authors.initials: S
authors.lastname: Ameratunga
authors.affiliation: Department of Public Health, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Polinder
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia ; Centre for Improvement of Population Health through E-records Research, Swansea University, Swansea, UK ; Public Health Wales NHS Trust, Swansea, Wales UK.
authors.forename: Ronan A
authors.initials: RA
authors.lastname: Lyons
authors.affiliation: Departments of Pediatrics and Epidemiology, and the Harborview Injury Prevention and Research Center, University of Washington, Seattle, USA.
authors.forename: Frederick P
authors.initials: FP
authors.lastname: Rivara
authors.affiliation: Research Centre for Injury Studies, Flinders University, Adelaide, South Australia.
authors.forename: James E
authors.initials: JE
authors.lastname: Harrison
keywords: Agreement; EQ-5D; Injury; Quality of life; SF-12