title: An empirical evaluation of the SF-12, SF-6D, EQ-5D and Michigan Hand Outcome Questionnaire in patients with rheumatoid arthritis of the hand.
abstract: BACKGROUND
  The aim of this study was to assess the psychometric properties, namely acceptability, validity, reliability, interpretability and responsiveness of the EuroQol EQ-5D (EQ-5D visual analogue (VAS) and EQ-5D (utility)), Short Form 12 Dimensions (SF-12), SF-6D and Michigan Hand Outcome Questionnaire (MHQ) in patients with rheumatoid arthritis (RA) of the hand.
  
  
  METHODS
  The empirical investigation was based upon data from a randomised controlled trial of 488 adults with rheumatoid arthritis who had pain and dysfunction of the hands and/or wrists. Participants completed the EQ-5D, SF-12 and MHQ at baseline and at 4 and 12 months follow up. Acceptability was measured using completion rates over time; construct validity using the "known groups" approach, based on pain troublesomeness; convergent validity using spearman's rho correlation (ρ); reliability using internal consistency (Cronbach's alpha); interpretability using minimal important differences (MID); and responsiveness using effect sizes and standardised response means (SRM) stratified by level of self-rated improvement in hand and wrist function or level of self-rated benefit and satisfaction from trial treatments.
  
  
  RESULTS
  At baseline, the study population had a mean age of 62.4 years, a mean MHQ score of 52.1 and included 76% women. The EQ-5D (utility) had the highest completion rates across time points. All instruments discriminated between pre-specified groups based on pain troublesomeness. Convergent validity analysis indicated that the MHQ score correlated strongly with the EQ-5D (ρ = 0.65) and SF-6D (ρ = 0.63) utility scores. The MHQ was most responsive at detecting change in indicators of RA pain severity between baseline and 4 months, whilst minimal important differences varied considerably across PROMs.
  
  
  CONCLUSIONS
  The instruments evaluated in this study displayed varying psychometric properties in the context of RA of the hand. The selection of a preferred instrument in evaluative studies should ultimately depend on the relative importance placed on individual psychometric properties and the importance placed on generation of health utilities for economic evaluation purposes.
authors.affiliation: Nuffield Department of Orthopaedic Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK. Melina.Dritsaki@ndorms.ox.ac.uk.
authors.forename: Melina
authors.initials: M
authors.lastname: Dritsaki
authors.affiliation: Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, UK.
authors.forename: Stavros
authors.initials: S
authors.lastname: Petrou
authors.affiliation: Department of Sport and Health Sciences, Oxford Brookes University, Oxford, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Williams
authors.affiliation: Nuffield Department of Orthopaedic Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Lamb
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis*; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008824:Michigan; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011594:Psychometrics / Q000295:instrumentation; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*
keywords: EQ-5D; Health Economics; Measurement properties; Outcome assessment; Rheumatoid arthritis; SF-6D; SF12; Utility measures