title: A self-administered rheumatoid arthritis disease activity index (RADAI) for epidemiologic research. Psychometric properties and correlation with parameters of disease activity.
abstract: OBJECTIVE
  To examine the psychometric properties and construct validity of a self-administered Rheumatoid Arthritis Disease Activity Index (RADAI).
  
  
  METHODS
  Five items of the Rapid Assessment of Disease Activity in Rheumatology (RADAR) questionnaire were aggregated into the RADAI and assessed for their factor loading, internal consistency, and construct validity.
  
  
  RESULTS
  In 55 patients with RA, the RADAI had a high internal consistency (Cronbach's alpha = 0.91) and correlated with physician's assessment of disease activity (r = 0.54, P < 0.01), the swollen joint count (r = 0.54, P < 0.01), and the C-reactive protein value (r = 0.43, P < 0.01).
  
  
  CONCLUSIONS
  The RADAI is a highly reliable and valid self-administered measure of disease activity for clinical, health services, and epidemiologic research. Its sensitivity to change in longitudinal studies needs further study.
authors.affiliation: Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: G
authors.initials: G
authors.lastname: Stucki
authors.forename: M H
authors.initials: MH
authors.lastname: Liang
authors.forename: S
authors.initials: S
authors.lastname: Stucki
authors.forename: P
authors.initials: P
authors.lastname: Brühlmann
authors.forename: B A
authors.initials: BA
authors.lastname: Michel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology* / Q000503:physiopathology* / Q000523:psychology; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D006801:Humans; D007596:Joints / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
chemical_list: D002097:C-Reactive Protein