title: The reliability and validity of the English version of the Evaluation of Daily Activity Questionnaire for people with rheumatoid arthritis.
abstract: OBJECTIVE
  The Evaluation of Daily Activity Questionnaire (EDAQ) includes 138 items in 14 domains identified as important by people with RA. The aim of this study was to test the validity and reliability of the English EDAQ.
  
  
  METHODS
  A total of 502 participants completed two questionnaires 3 weeks apart. The first consisted of the EDAQ, HAQ, RA Quality of Life (RAQoL) and the Medical Outcomes Scale (MOS) 36-item Short-Form Health Survey (SF-36v2), and the second consisted of the EDAQ only. The 14 EDAQ domains were tested for: unidimensionality-using confirmatory factor analysis; fit, response dependency, invariance across groups (differential item functioning)-using Rasch analysis; internal consistency [Person Separation Index (PSI)]; concurrent validity-by correlations with the HAQ, SF-36v2 and RAQoL; and test-retest reliability (Spearman's correlations).
  
  
  RESULTS
  Confirmatory factor analysis of the 14 EDAQ domains indicated unidimensionality, after adjustment for local dependency in each domain. All domains achieved a root mean square error of approximation <0.10 and satisfied Rasch model expectations for local dependency. DIF by age, gender and employment status was largely absent. The PSI was consistent with individual use (PSI = 0.94 for all 14 domains). For all domains, except Caring, concurrent validity was good: HAQ (rs = 0.72-0.91), RAQoL (rs = 0.67-0.82) and SF36v2 Physical Function scale (rs = -0.60 to -0.84) and test-retest reliability was good (rs = 0.70-0.89).
  
  
  CONCLUSIONS
  Analysis supported a 14-domain, two-component structure (Self care and Mobility) of the EDAQ, where each domain, and both components, satisfied Rasch model requirements, and have robust reliability and validity.
authors: Centre for Health Sciences Research, School of Health Sciences, University of Salford, Salford, a.hammond@salford.ac.uk hammond116@btinternet.com.
authors: Alison
authors: A
authors: Hammond
authors: Academic Department of Rehabilitation Medicine, Section of Musculoskeletal Disease, Leeds Institute of Molecular Medicine, Faculty of Medicine and Health, The University of Leeds, Leeds.
authors: Alan
authors: A
authors: Tennant
authors: Stroke & Vascular Research Centre, School of Nursing, Midwifery & Social Work, University of Manchester, Manchester.
authors: Sarah F
authors: SF
authors: Tyson
authors: Institute of Neuroscience and Physiology, Rehabilitation Medicine, Sahlgrenska Academy, Göteborg University, Sweden and.
authors: Ulla
authors: U
authors: Nordenskiöld
authors: National Rheumatoid Arthritis Society, Derby, UK.
authors: Ruth
authors: R
authors: Hawkins
authors: Centre for Health Sciences Research, School of Health Sciences, University of Salford, Salford.
authors: Yeliz
authors: Y
authors: Prior
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D004185:Disability Evaluation; D005260:Female; D006304:Health Status; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*; D006113:United Kingdom
keywords: Rasch analysis; activities of daily living; outcome research; rheumatoid arthritis