title: The minimally important difference for the Japanese version of the health assessment questionnaire in patients with rheumatoid arthritis in daily practice.
abstract: OBJECTIVE
  To validate the minimally important difference (MID) of physical function using the Japanese version of the Health Assessment Questionnaire (J-HAQ) in a cohort of rheumatoid arthritis (RA).
  
  
  METHODS
  Patients who participated in a cohort study in both October 2008 and April 2009 were analyzed. Patients self-rated their change in overall status over 6 months using a 5-point Likert scale ("much better", "somewhat better", "same", "somewhat worse", or "much worse"). The MID for J-HAQ score was defined as the mean J-HAQ score change in patients who rated themselves "somewhat better". An effect size (ES) of 0.2-0.5 was considered to be suitable for MID.
  
  
  RESULTS
  A total of 4560 patients were analyzed. The mean (standard deviation [SD]) MID for J-HAQ score was -0.06 (0.29), corresponding to an ES of 0.08. As exploratory analysis, 1999 patients with a J-HAQ score ≥0.5 and 28-joint disease activity score (DAS28) ≥ 2.6 at baseline were assessed. The mean (SD) MID for J-HAQ score of these patients was 0.13 (0.01), corresponding to an ES of 0.21.
  
  
  CONCLUSIONS
  The MID for J-HAQ score was 0.13 in patients with baseline J-HAQ score ≥0.5 and DAS28 ≥ 2.6. The MID for J-HAQ score was influenced by disease status and functional disability.
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Kumi
authors: K
authors: Shidara
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Ayako
authors: A
authors: Nakajima
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Eisuke
authors: E
authors: Inoue
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Daisuke
authors: D
authors: Hoshi
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Naoki
authors: N
authors: Sugimoto
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Yohei
authors: Y
authors: Seto
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Eiichi
authors: E
authors: Tanaka
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Katsunori
authors: K
authors: Ikari
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Atsuo
authors: A
authors: Taniguchi
authors: a Department of Rhumatology , Institute of Rheumatology, Tokyo Women's Medical University , Tokyo , Japan.
authors: Hisashi
authors: H
authors: Yamanaka
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D011795:Surveys and Questionnaires / Q000592:standards*
keywords: Functional disability; Health assessment questionnaire; Minimally important difference; Patient-reported outcomes; Rheumatoid arthritis